diff --git a/reactos/boot/freeldr/freeldr/arch/i386/hardware.c b/reactos/boot/freeldr/freeldr/arch/i386/hardware.c
index 6b3d7a4dcc4..d4654ccd138 100644
--- a/reactos/boot/freeldr/freeldr/arch/i386/hardware.c
+++ b/reactos/boot/freeldr/freeldr/arch/i386/hardware.c
@@ -433,11 +433,27 @@ static LONG DiskOpen(CHAR* Path, OPENMODE OpenMode, ULONG* FileId)
     ULONGLONG SectorOffset = 0;
     ULONGLONG SectorCount = 0;
     PARTITION_TABLE_ENTRY PartitionTableEntry;
+    GEOMETRY Geometry;
+    EXTENDED_GEOMETRY ExtGeometry;
     CHAR FileName[1];
 
     if (!DissectArcPath(Path, FileName, &DriveNumber, &DrivePartition))
         return EINVAL;
-    SectorSize = (DrivePartition == 0xff ? 2048 : 512);
+
+    ExtGeometry.Size = sizeof(EXTENDED_GEOMETRY);
+    if (DiskGetExtendedDriveParameters(DriveNumber, &ExtGeometry, ExtGeometry.Size))
+    {
+        SectorSize = ExtGeometry.BytesPerSector;
+        SectorCount = ExtGeometry.Sectors;
+    }
+    else if (MachDiskGetDriveGeometry(DriveNumber, &Geometry))
+    {
+        SectorSize = Geometry.BytesPerSector;
+        SectorCount = Geometry.Sectors;
+    }
+    else
+        return EINVAL;
+
     if (DrivePartition != 0xff && DrivePartition != 0)
     {
         if (!DiskGetPartitionEntry(DriveNumber, DrivePartition, &PartitionTableEntry))
@@ -445,10 +461,6 @@ static LONG DiskOpen(CHAR* Path, OPENMODE OpenMode, ULONG* FileId)
         SectorOffset = PartitionTableEntry.SectorCountBeforePartition;
         SectorCount = PartitionTableEntry.PartitionSectorCount;
     }
-    else
-    {
-        SectorCount = 0; /* FIXME */
-    }
 
     Context = MmHeapAlloc(sizeof(DISKCONTEXT));
     if (!Context)