Index: fstub/disksup.c
===================================================================
--- fstub/disksup.c	(revision 39028)
+++ fstub/disksup.c	(working copy)
@@ -47,7 +47,9 @@
                 IN UCHAR DriveType,
                 IN ULONG Signature,
                 IN LARGE_INTEGER StartingOffset,
-                IN HANDLE hKey)
+                IN HANDLE hKey,
+                IN PUNICODE_STRING BootDevice,
+                OUT PUCHAR NtSystemPath)
 {
     WCHAR DriveNameBuffer[16];
     UNICODE_STRING DriveName;
@@ -128,6 +130,11 @@
             DPRINT1("ZwCreateValueKey failed for %wZ, status=%x\n", &DriveName, Status);
         }
     }
+
+    if (RtlCompareUnicodeString(PartitionName,BootDevice,FALSE) == 0)
+    {
+        *NtSystemPath = 'A' + DriveNumber;
+    }
     return TRUE;
 }
 
@@ -420,7 +427,12 @@
     PKEY_VALUE_PARTIAL_INFORMATION PartialInformation;
     PREG_DISK_MOUNT_INFO DiskMountInfo;
     ULONG RDiskCount;
+    UNICODE_STRING BootDevice;
 
+    Status = RtlAnsiStringToUnicodeString(&BootDevice,
+                                          NtDeviceName,
+                                          TRUE);
+
     DPRINT("xHalIoAssignDriveLetters()\n");
 
     ConfigInfo = IoGetConfigurationInformation();
@@ -612,7 +624,9 @@
                                             DOSDEVICE_DRIVE_FIXED,
                                             DiskMountInfo->Signature,
                                             DiskMountInfo->StartingOffset,
-                                            NULL);
+                                            NULL,
+                                            &BootDevice,
+                                            NtSystemPath);
                                         /* Mark the partition as assigned */
                                         LayoutArray[i]->PartitionEntry[j].RewritePartition = TRUE;
                                     }
@@ -662,7 +676,9 @@
                             DOSDEVICE_DRIVE_FIXED,
                             LayoutArray[DiskNumber]->Signature,
                             LayoutArray[DiskNumber]->PartitionEntry[j].StartingOffset,
-                            hKey);
+                            hKey,
+                            &BootDevice,
+                            NtSystemPath);
                         /* Mark the partition as assigned */
                         LayoutArray[DiskNumber]->PartitionEntry[j].RewritePartition = TRUE;
                     }
@@ -702,7 +718,9 @@
                         DOSDEVICE_DRIVE_FIXED,
                         LayoutArray[DiskNumber]->Signature,
                         LayoutArray[DiskNumber]->PartitionEntry[j].StartingOffset,
-                        hKey);
+                        hKey,
+                        &BootDevice,
+                        NtSystemPath);
                     /* Mark the partition as assigned */
                     LayoutArray[DiskNumber]->PartitionEntry[j].RewritePartition = TRUE;
                 }
@@ -741,7 +759,9 @@
                         DOSDEVICE_DRIVE_FIXED,
                         LayoutArray[DiskNumber]->Signature,
                         LayoutArray[DiskNumber]->PartitionEntry[j].StartingOffset,
-                        hKey);
+                        hKey,
+                        &BootDevice,
+                        NtSystemPath);
                     /* Mark the partition as assigned */
                     LayoutArray[DiskNumber]->PartitionEntry[j].RewritePartition = TRUE;
                 }
@@ -776,7 +796,9 @@
                         DOSDEVICE_DRIVE_FIXED,
                         LayoutArray[DiskNumber]->Signature,
                         LayoutArray[DiskNumber]->PartitionEntry[j].StartingOffset,
-                        hKey);
+                        hKey,
+                        &BootDevice,
+                        NtSystemPath);
                     /* Mark the partition as assigned */
                     LayoutArray[DiskNumber]->PartitionEntry[j].RewritePartition = TRUE;
                 }
@@ -812,7 +834,9 @@
                         DOSDEVICE_DRIVE_FIXED,
                         LayoutArray[DiskNumber]->Signature,
                         LayoutArray[DiskNumber]->PartitionEntry[j].StartingOffset,
-                        hKey);
+                        hKey,
+                        &BootDevice,
+                        NtSystemPath);
                     /* Mark the partition as assigned */
                     LayoutArray[DiskNumber]->PartitionEntry[j].RewritePartition = TRUE;
                 }
@@ -844,7 +868,9 @@
                     DOSDEVICE_DRIVE_REMOVABLE,
                     0,
                     RtlConvertLongToLargeInteger(0),
-                    hKey);
+                    hKey,
+                    &BootDevice,
+                    NtSystemPath);
             }
         }
     }
@@ -875,7 +901,9 @@
             DOSDEVICE_DRIVE_REMOVABLE,
             0,
             RtlConvertLongToLargeInteger(0),
-            hKey);
+            hKey,
+            &BootDevice,
+            NtSystemPath);
     }
 
     /* Assign cdrom drives */
@@ -895,7 +923,9 @@
             DOSDEVICE_DRIVE_CDROM,
             0,
             RtlConvertLongToLargeInteger(0),
-            hKey);
+            hKey,
+            &BootDevice,
+            NtSystemPath);
     }
 
     /* Anything else to do? */
Index: io/iomgr/arcname.c
===================================================================
--- io/iomgr/arcname.c	(revision 39028)
+++ io/iomgr/arcname.c	(working copy)
@@ -114,8 +114,6 @@
     /* Return whether this is the CD or not */
     if ((InitIsWinPEMode) || (ExpInTextModeSetup))
     {
-        /* Hack until IoAssignDriveLetters is fixed */
-        swprintf(SharedUserData->NtSystemRoot, L"%c:\\%hs", 'C' + DeviceNumber, RosSysPath);
         return TRUE;
     }