|Might try fdisk.|
You might try a live linux or live xp cd on that drive to see exactly what is on it and how it is used. It may not be bootable even if you make it active. Might find WIM file that you could use in a custom dvd. Might be a renamed ghost image file that can run with ghost even. (some toshibas do that)
Whatever I you decide, might be sure to copy all that data off before you bork it more. (sorry just facts)
The best way would be to order the factory dvd's to return it to OEM state I'd think.
Playing to the angels
Les Paul (1915-2009)