This has been happening to my Medion for a while now, but I couldn't be bothered fixing it.
It has been booting from the CD okay, till I took the CD out to put another one in for the printer. I did an XP repair and lost a few things.....
I took the printer CD out and closed the ROM door, forgot about the booting problem, now I can't get the damned door open again and it won't boot without it.