diff --git a/boot/freeldr/freeldr/arch/i386/hwdisk.c b/boot/freeldr/freeldr/arch/i386/hwdisk.c
index 9f623a36fe6..ef13c24bbe4 100644
--- a/boot/freeldr/freeldr/arch/i386/hwdisk.c
+++ b/boot/freeldr/freeldr/arch/i386/hwdisk.c
@@ -63,8 +63,16 @@ DiskGetFileInformation(ULONG FileId, FILEINFORMATION* Information)
     DISKCONTEXT* Context = FsGetDeviceSpecific(FileId);
 
     RtlZeroMemory(Information, sizeof(*Information));
-    Information->EndingAddress.QuadPart = Context->SectorCount * Context->SectorSize;
-    Information->CurrentAddress.QuadPart = Context->SectorNumber * Context->SectorSize;
+
+    /*
+     * The ARC specification mentions that for partitions, StartingAddress and
+     * EndingAddress are the start and end positions of the partition in terms
+     * of byte offsets from the start of the disk.
+     * CurrentAddress is the current offset into (i.e. relative to) the partition.
+     */
+    Information->StartingAddress.QuadPart = Context->SectorOffset * Context->SectorSize;
+    Information->EndingAddress.QuadPart   = (Context->SectorOffset + Context->SectorCount) * Context->SectorSize;
+    Information->CurrentAddress.QuadPart  = Context->SectorNumber * Context->SectorSize;
 
     return ESUCCESS;
 }
@@ -113,12 +121,21 @@ DiskOpen(CHAR* Path, OPENMODE OpenMode, ULONG* FileId)
         SectorOffset = PartitionTableEntry.SectorCountBeforePartition;
         SectorCount = PartitionTableEntry.PartitionSectorCount;
     }
-#if 0 // FIXME: Investigate
     else
     {
-        SectorCount = 0; /* FIXME */
+        GEOMETRY Geometry;
+        if (!MachDiskGetDriveGeometry(DriveNumber, &Geometry))
+            return EINVAL;
+
+        if (SectorSize != Geometry.BytesPerSector)
+        {
+            ERR("SectorSize (%lu) != Geometry.BytesPerSector (%lu), expect problems!\n",
+                SectorSize, Geometry.BytesPerSector);
+        }
+
+        SectorOffset = 0;
+        SectorCount = (ULONGLONG)Geometry.Cylinders * Geometry.Heads * Geometry.Sectors;
     }
-#endif
 
     Context = FrLdrTempAlloc(sizeof(DISKCONTEXT), TAG_HW_DISK_CONTEXT);
     if (!Context)
@@ -147,7 +164,7 @@ DiskRead(ULONG FileId, VOID* Buffer, ULONG N, ULONG* Count)
 
     TotalSectors = (N + Context->SectorSize - 1) / Context->SectorSize;
     MaxSectors   = DiskReadBufferSize / Context->SectorSize;
-    SectorOffset = Context->SectorNumber + Context->SectorOffset;
+    SectorOffset = Context->SectorOffset + Context->SectorNumber;
 
     // If MaxSectors is 0, this will lead to infinite loop.
     // In release builds assertions are disabled, however we also have sanity checks in DiskOpen()
@@ -189,13 +206,18 @@ static ARC_STATUS
 DiskSeek(ULONG FileId, LARGE_INTEGER* Position, SEEKMODE SeekMode)
 {
     DISKCONTEXT* Context = FsGetDeviceSpecific(FileId);
+    ULONGLONG SectorNumber;
 
     if (SeekMode != SeekAbsolute)
         return EINVAL;
     if (Position->LowPart & (Context->SectorSize - 1))
         return EINVAL;
 
-    Context->SectorNumber = Position->QuadPart / Context->SectorSize;
+    SectorNumber = Position->QuadPart / Context->SectorSize;
+    if (SectorNumber >= Context->SectorCount)
+        return EINVAL;
+
+    Context->SectorNumber = SectorNumber;
     return ESUCCESS;
 }
 
diff --git a/boot/freeldr/freeldr/arch/i386/machpc.c b/boot/freeldr/freeldr/arch/i386/machpc.c
index d95f70f6a25..712a0575b44 100644
--- a/boot/freeldr/freeldr/arch/i386/machpc.c
+++ b/boot/freeldr/freeldr/arch/i386/machpc.c
@@ -147,7 +147,7 @@ PcGetHarddiskConfigurationData(UCHAR DriveNumber, ULONG* pSize)
         DiskGeometry->SectorsPerTrack = ExtGeometry.SectorsPerTrack;
         DiskGeometry->NumberOfHeads = ExtGeometry.Heads;
     }
-    else if (MachDiskGetDriveGeometry(DriveNumber, &Geometry))
+    else if (PcDiskGetDriveGeometry(DriveNumber, &Geometry))
     {
         DiskGeometry->BytesPerSector = Geometry.BytesPerSector;
         DiskGeometry->NumberOfCylinders = Geometry.Cylinders;
diff --git a/boot/freeldr/freeldr/arch/i386/machxbox.c b/boot/freeldr/freeldr/arch/i386/machxbox.c
index 2bdee5f0f45..7b12084c294 100644
--- a/boot/freeldr/freeldr/arch/i386/machxbox.c
+++ b/boot/freeldr/freeldr/arch/i386/machxbox.c
@@ -133,7 +133,7 @@ XboxGetHarddiskConfigurationData(UCHAR DriveNumber, ULONG* pSize)
     /* Get the disk geometry */
     //ExtGeometry.Size = sizeof(EXTENDED_GEOMETRY);
 
-    if (MachDiskGetDriveGeometry(DriveNumber, &Geometry))
+    if (XboxDiskGetDriveGeometry(DriveNumber, &Geometry))
     {
         DiskGeometry->BytesPerSector = Geometry.BytesPerSector;
         DiskGeometry->NumberOfCylinders = Geometry.Cylinders;
diff --git a/boot/freeldr/freeldr/arch/i386/pcdisk.c b/boot/freeldr/freeldr/arch/i386/pcdisk.c
index 87c21fc3b64..f9fc4f0c1ba 100644
--- a/boot/freeldr/freeldr/arch/i386/pcdisk.c
+++ b/boot/freeldr/freeldr/arch/i386/pcdisk.c
@@ -240,9 +240,11 @@ static BOOLEAN PcDiskReadLogicalSectorsCHS(UCHAR DriveNumber, ULONGLONG SectorNu
     TRACE("PcDiskReadLogicalSectorsCHS()\n");
 
     /* Get the drive geometry */
-    if (!MachDiskGetDriveGeometry(DriveNumber, &DriveGeometry) ||
-        DriveGeometry.Sectors == 0 ||
-        DriveGeometry.Heads == 0)
+    //
+    // TODO: Cache this information for the given drive.
+    //
+    if (!PcDiskGetDriveGeometry(DriveNumber, &DriveGeometry) ||
+        DriveGeometry.Sectors == 0 || DriveGeometry.Heads == 0)
     {
         return FALSE;
     }
diff --git a/boot/freeldr/freeldr/disk/scsiport.c b/boot/freeldr/freeldr/disk/scsiport.c
index 21b7390e021..92b032ea574 100644
--- a/boot/freeldr/freeldr/disk/scsiport.c
+++ b/boot/freeldr/freeldr/disk/scsiport.c
@@ -178,8 +178,16 @@ static ARC_STATUS DiskGetFileInformation(ULONG FileId, FILEINFORMATION* Informat
     DISKCONTEXT* Context = FsGetDeviceSpecific(FileId);
 
     RtlZeroMemory(Information, sizeof(*Information));
-    Information->EndingAddress.QuadPart = Context->SectorCount * Context->SectorSize;
-    Information->CurrentAddress.QuadPart = Context->SectorNumber * Context->SectorSize;
+
+    /*
+     * The ARC specification mentions that for partitions, StartingAddress and
+     * EndingAddress are the start and end positions of the partition in terms
+     * of byte offsets from the start of the disk.
+     * CurrentAddress is the current offset into (i.e. relative to) the partition.
+     */
+    Information->StartingAddress.QuadPart = Context->SectorOffset * Context->SectorSize;
+    Information->EndingAddress.QuadPart   = (Context->SectorOffset + Context->SectorCount) * Context->SectorSize;
+    Information->CurrentAddress.QuadPart  = Context->SectorNumber * Context->SectorSize;
 
     return ESUCCESS;
 }
@@ -276,7 +284,7 @@ static ARC_STATUS DiskRead(ULONG FileId, VOID* Buffer, ULONG N, ULONG* Count)
 
     /* Read full sectors */
     ASSERT(Context->SectorNumber < 0xFFFFFFFF);
-    Lba = (ULONG)Context->SectorNumber;
+    Lba = (ULONG)(Context->SectorOffset + Context->SectorNumber);
     if (FullSectors > 0)
     {
         Srb = ExAllocatePool(PagedPool, sizeof(SCSI_REQUEST_BLOCK));
@@ -365,13 +373,18 @@ static ARC_STATUS DiskRead(ULONG FileId, VOID* Buffer, ULONG N, ULONG* Count)
 static ARC_STATUS DiskSeek(ULONG FileId, LARGE_INTEGER* Position, SEEKMODE SeekMode)
 {
     DISKCONTEXT* Context = FsGetDeviceSpecific(FileId);
+    ULONGLONG SectorNumber;
 
     if (SeekMode != SeekAbsolute)
         return EINVAL;
     if (Position->QuadPart & (Context->SectorSize - 1))
         return EINVAL;
 
-    Context->SectorNumber = Position->QuadPart / Context->SectorSize;
+    SectorNumber = Position->QuadPart / Context->SectorSize;
+    if (SectorNumber >= Context->SectorCount)
+        return EINVAL;
+
+    Context->SectorNumber = SectorNumber;
     return ESUCCESS;
 }
 
diff --git a/boot/freeldr/freeldr/lib/fs/fat.c b/boot/freeldr/freeldr/lib/fs/fat.c
index 63a1283a439..7dad4f2f516 100644
--- a/boot/freeldr/freeldr/lib/fs/fat.c
+++ b/boot/freeldr/freeldr/lib/fs/fat.c
@@ -1570,7 +1570,7 @@ const DEVVTBL* FatMount(ULONG DeviceId)
         FrLdrTempFree(Volume, TAG_FAT_VOLUME);
         return NULL;
     }
-    SectorCount.QuadPart = FileInformation.EndingAddress.QuadPart;
+    SectorCount.QuadPart = (FileInformation.EndingAddress.QuadPart - FileInformation.StartingAddress.QuadPart);
     SectorCount.QuadPart /= SECTOR_SIZE;
 
     //