diff --git a/bootloader/gigabeat-s.c b/bootloader/gigabeat-s.c
index 9c5ad93d1f..c29265ddad 100644
--- a/bootloader/gigabeat-s.c
+++ b/bootloader/gigabeat-s.c
@@ -71,11 +71,15 @@ static bool pause_if_button_pressed(bool pre_usb)
         if (pre_usb && !usb_plugged())
             return false;
 
-        /* Exit if no button or only the menu (settings reset) button */
+        /* Exit if no button or only select buttons that have other
+         * functions */
         switch (button)
         {
-        case BUTTON_MENU:
-        case BUTTON_NONE:
+        case USB_BL_INSTALL_MODE_BTN:
+            if (!pre_usb)
+                break;    /* Only before USB detect */
+        case BUTTON_MENU: /* Settings reset */
+        case BUTTON_NONE: /* Nothing pressed */
             return true;
         }
 
diff --git a/firmware/export/config/gigabeats.h b/firmware/export/config/gigabeats.h
index fcfa274314..cf560aa35f 100644
--- a/firmware/export/config/gigabeats.h
+++ b/firmware/export/config/gigabeats.h
@@ -190,8 +190,17 @@
 
 /* define this if the unit can be powered or charged via USB */
 #define HAVE_USB_POWER
-#define USBPOWER_BUTTON     BUTTON_MENU
-#define USBPOWER_BTN_IGNORE BUTTON_POWER
+#define USBPOWER_BUTTON             BUTTON_MENU
+
+#ifndef BOOTLOADER
+#define USBPOWER_BTN_IGNORE         BUTTON_POWER
+#else
+/* Disable charging-only mode detection in bootloader */
+#define USBPOWER_BTN_IGNORE         (BUTTON_MAIN | BUTTON_REMOTE)
+#endif
+
+/* Button that exposures boot partition rather than data during session */
+#define USB_BL_INSTALL_MODE_BTN     BUTTON_VOL_DOWN
 
 /* define this if the unit has a battery switch or battery can be removed
  * when running */
diff --git a/firmware/target/arm/imx31/gigabeat-s/usb-gigabeat-s.c b/firmware/target/arm/imx31/gigabeat-s/usb-gigabeat-s.c
index 016f24fc48..c52a9a6dec 100644
--- a/firmware/target/arm/imx31/gigabeat-s/usb-gigabeat-s.c
+++ b/firmware/target/arm/imx31/gigabeat-s/usb-gigabeat-s.c
@@ -19,7 +19,6 @@
  *
  ****************************************************************************/
 #include "config.h"
-#include "cpu.h"
 #include "system.h"
 #include "kernel.h"
 #include "ata.h"
@@ -31,8 +30,10 @@
 #include "ccm-imx31.h"
 #include "avic-imx31.h"
 #include "power-gigabeat-s.h"
+#include <string.h>
 
 static int usb_status = USB_EXTRACTED;
+static bool bootloader_install_mode = false;
 
 static void enable_transceiver(bool enable)
 {
@@ -106,6 +107,16 @@ void usb_enable(bool on)
 
 void usb_attach(void)
 {
+    bootloader_install_mode = false;
+
+    if (usb_core_driver_enabled(USB_DRIVER_MASS_STORAGE))
+    {
+        /* Check if this will be bootloader install mode, exposing the
+         * boot partition instead of the data partition */
+        bootloader_install_mode =
+            (button_status() & USB_BL_INSTALL_MODE_BTN) != 0;
+    }
+
     usb_drv_attach();
 }
 
@@ -133,3 +144,34 @@ void usb_drv_usb_detect_event(void)
     if (usb_drv_powered())
         usb_status_event(USB_INSERTED);
 }
+
+/* Called when reading the MBR */
+void usb_fix_mbr(unsigned char *mbr)
+{
+    unsigned char* p = mbr + 0x1be;
+    char tmp[16];
+
+    /* The Gigabeat S factory partition table contains invalid values for the
+       "active" flag in the MBR.  This prevents at least the Linux kernel
+       from accepting the partition table, so we fix it on-the-fly. */
+    p[0x00] &= 0x80;
+    p[0x10] &= 0x80;
+    p[0x20] &= 0x80;
+    p[0x30] &= 0x80;
+
+    if (bootloader_install_mode)
+        return;
+
+    /* Windows ignores the partition flags and mounts the first partition it
+       sees when the device reports itself as removable. Swap the partitions
+       so the data partition appears to be partition 0. Mark the boot
+       partition 0 as hidden and make it partition 1. */
+
+    /* Mark the first partition as hidden */
+    p[0x04] |= 0x10;
+
+    /* Swap first and second partitions */
+    memcpy(tmp, &p[0x00], 16);
+    memcpy(&p[0x00], &p[0x10], 16);
+    memcpy(&p[0x10], tmp, 16);
+}
diff --git a/firmware/target/arm/imx31/gigabeat-s/usb-target.h b/firmware/target/arm/imx31/gigabeat-s/usb-target.h
index c93400ca0b..7931058241 100644
--- a/firmware/target/arm/imx31/gigabeat-s/usb-target.h
+++ b/firmware/target/arm/imx31/gigabeat-s/usb-target.h
@@ -30,4 +30,17 @@ void usb_init_device(void);
 /* Read the immediate state of the cable from the PMIC */
 bool usb_plugged(void);
 
+/** Sector read/write filters **/
+
+/* Filter some things in the MBR - see usb-gigabeat-s.c */
+void usb_fix_mbr(unsigned char *mbr);
+#define USBSTOR_READ_SECTORS_FILTER() \
+    ({ if (cur_cmd.sector == 0) \
+            usb_fix_mbr(cur_cmd.data[cur_cmd.data_select]); \
+    0; })
+
+/* Disallow MBR writes entirely since it was "fixed" in usb_fix_mbr */
+#define USBSTOR_WRITE_SECTORS_FILTER() \
+    ({ cur_cmd.sector != 0 ? 0 : -1; })
+
 #endif /* USB_TARGET */
diff --git a/firmware/usbstack/usb_storage.c b/firmware/usbstack/usb_storage.c
index 005697f6fa..1ff3b1ec4c 100644
--- a/firmware/usbstack/usb_storage.c
+++ b/firmware/usbstack/usb_storage.c
@@ -32,6 +32,8 @@
 #include "usb_storage.h"
 #include "timefuncs.h"
 
+/* For sector filter macro definitions */
+#include "usb-target.h"
 
 /* Enable the following define to export only the SD card slot. This
  * is useful for USBCV MSC tests, as those are destructive.
@@ -47,6 +49,15 @@
 #define SECTOR_SIZE 512
 #endif
 
+/* These defaults allow the operation */
+#ifndef USBSTOR_READ_SECTORS_FILTER
+#define USBSTOR_READ_SECTORS_FILTER() ({ 0; })
+#endif
+
+#ifndef USBSTOR_WRITE_SECTORS_FILTER
+#define USBSTOR_WRITE_SECTORS_FILTER() ({ 0; }) 
+#endif
+
 /* the ARC driver currently supports up to 64k USB transfers. This is
  * enough for efficient mass storage support, as commonly host OSes
  * don't do larger SCSI transfers anyway, so larger USB transfers
@@ -342,23 +353,6 @@ static void yearday_to_daymonth(int yd, int y, int *d, int *m)
     *m = i;
 }
 
-#ifdef TOSHIBA_GIGABEAT_S
-
-/* The Gigabeat S factory partition table contains invalid values for the
-   "active" flag in the MBR.  This prevents at least the Linux kernel from
-   accepting the partition table, so we fix it on-the-fly. */
-
-static void fix_mbr(unsigned char* mbr)
-{
-    unsigned char* p = mbr + 0x1be;
-
-    p[0x00] &= 0x80;
-    p[0x10] &= 0x80;
-    p[0x20] &= 0x80;
-    p[0x30] &= 0x80;
-}
-#endif
-
 static bool check_disk_present(IF_MD_NONVOID(int volume))
 {
 #ifdef USB_USE_RAMDISK
@@ -491,14 +485,7 @@ void usb_storage_init_connection(void)
 
     int i;
     for(i=0;i<storage_num_drives();i++) {
-#ifdef TOSHIBA_GIGABEAT_S
-        /* As long as the Gigabeat S is a non-removable device, we need
-           to mark the device as locked to avoid usb_storage_try_release_ata()
-           to leave MSC mode while the device is in use */
-        locked[i] = true;
-#else
         locked[i] = false;
-#endif
         ejected[i] = !check_disk_present(IF_MD(i));
         queue_broadcast(SYS_USB_LUN_LOCKED, (i<<16)+0);
     }
@@ -549,10 +536,15 @@ void usb_storage_transfer_complete(int ep,int dir,int status,int length)
                         cur_cmd.data[cur_cmd.data_select],
                         MIN(WRITE_BUFFER_SIZE/SECTOR_SIZE, cur_cmd.count)*SECTOR_SIZE);
 #else
-                int result = storage_write_sectors(IF_MD2(cur_cmd.lun,)
+                int result = USBSTOR_WRITE_SECTORS_FILTER();
+
+                if (result == 0) {
+                    result = storage_write_sectors(IF_MD2(cur_cmd.lun,)
                         cur_cmd.sector,
                         MIN(WRITE_BUFFER_SIZE/SECTOR_SIZE, cur_cmd.count),
                         cur_cmd.data[cur_cmd.data_select]);
+                }
+
                 if(result != 0) {
                     send_csw(UMS_STATUS_FAIL);
                     cur_sense_data.sense_key=SENSE_MEDIUM_ERROR;
@@ -725,6 +717,11 @@ bool usb_storage_control_request(struct usb_ctrlrequest* req, unsigned char* des
 
 static void send_and_read_next(void)
 {
+    int result = USBSTOR_READ_SECTORS_FILTER();
+
+    if(result != 0 && cur_cmd.last_result == 0)
+        cur_cmd.last_result = result;
+
     send_block_data(cur_cmd.data[cur_cmd.data_select],
                     MIN(READ_BUFFER_SIZE,cur_cmd.count*SECTOR_SIZE));
 
@@ -742,7 +739,7 @@ static void send_and_read_next(void)
                 ramdisk_buffer + cur_cmd.sector*SECTOR_SIZE,
                 MIN(READ_BUFFER_SIZE/SECTOR_SIZE, cur_cmd.count)*SECTOR_SIZE);
 #else
-        int result = storage_read_sectors(IF_MD2(cur_cmd.lun,)
+        result = storage_read_sectors(IF_MD2(cur_cmd.lun,)
                 cur_cmd.sector,
                 MIN(READ_BUFFER_SIZE/SECTOR_SIZE, cur_cmd.count),
                 cur_cmd.data[cur_cmd.data_select]);
@@ -1104,12 +1101,6 @@ static void handle_scsi(struct command_block_wrapper* cbw)
                         cur_cmd.sector,
                         MIN(READ_BUFFER_SIZE/SECTOR_SIZE, cur_cmd.count),
                         cur_cmd.data[cur_cmd.data_select]);
-
-#ifdef TOSHIBA_GIGABEAT_S
-                if(cur_cmd.sector == 0) {
-                    fix_mbr(cur_cmd.data[cur_cmd.data_select]);
-                }
-#endif
 #endif
                 send_and_read_next();
             }
@@ -1262,9 +1253,5 @@ static void fill_inquiry(IF_MD_NONVOID(int lun))
     tb.inquiry->Versions = 4; /* SPC-2 */
     tb.inquiry->Format = 2; /* SPC-2/3 inquiry format */
 
-#ifdef TOSHIBA_GIGABEAT_S
-    tb.inquiry->DeviceTypeModifier = 0;
-#else
     tb.inquiry->DeviceTypeModifier = DEVICE_REMOVABLE;
-#endif
 }