Index: boot/freeldr/bootsect/dosmbr.S
===================================================================
--- boot/freeldr/bootsect/dosmbr.S	(revision 66268)
+++ boot/freeldr/bootsect/dosmbr.S	(working copy)
@@ -51,7 +51,7 @@
     lea di, [bp + HEX(1be)] // start of partition table
 test_next_for_active:
     test byte ptr ds:[di], HEX(80)
-    jne active_partition_found
+    jnz active_partition_found
     add di, 16                    // next table
     cmp di, HEX(07c00) + HEX(1fe) // scanned beyond end of table ??
     jb test_next_for_active
@@ -100,6 +100,25 @@
  * OUT:CARRY
  *****************************/
 read_boot_sector:
+
+    /* Save registers */
+    pusha
+
+    /* int 13h, function 8 = Get drive parameters
+       To check, whether the drive presented in dl is valid */
+    mov ah, 8
+    xor di, di
+    int HEX(13)
+
+    /* Restore registers */
+    popa
+
+    /* If there was an error, force drive to 0x80 (first HDD) */
+    jnc drive_ok
+    mov dl, HEX(80)
+
+drive_ok:
+
     /* check for LBA support */
     mov bx, HEX(55aa)
     mov ah, HEX(41)