[ubuntu] Master boot record problem (I think)

[-rchown]

Here's my situation:
I have ubuntu on my 320gb hard drive
i HAD full-functioning mac os x leopard 10.5.3 with graphics, sound, and networking (long story)
while on os x, i formatted my windows partition for a time machine backup partition.
i restart, and this is the beginning of the shitty day ive had today (yes, i know its fantastic, isnt it!)
so i put my genuine windows vista cd i bought in the disk drive, it goes to the black screen and says "missing operating system"
then i put in my leopard install disk, once again, the happy little black screen!
THEN i go into my brothers room, pull apart his computer, take my hard drive out, put it in his computer, formatted my hard drive, and you'd think everything would be better right?
i install ubuntu while the hard drive is in his computer, thought i may as well.
and now, all i have, ALL i have, is ubuntu
oh yeah, and a computer that wont boot from any disk, or hard drive, except ubuntu
so now im on ubuntu, surfing the interwebs for a solution, cant find one.
i would really appreciate if someone would tell me how to get at least vista back on my computer.