First, get a Vista reinstall disk some way or another. You can sometimes request one from Microsoft, or your computer manufacturer. Anyway, once you've got the disk, put it in the machine and blank the whole hard drive. Just get rid of everything. Then, you can reinstall Vista, and then reinstall Ubuntu. And, next time, don't delete the root linux partitions! Also, next time you buy a computer, refuse to buy one that doesn't come with a recovery disk!

I had a similar problem once, only it occurred under slightly different circumstances. I installed Linux FIRST rather than Windows, so when I installed Vista, it lost GRUB somehow. Then, after fiddling with the computer for another three hours, I somehow managed to bring GRUB back (I forget how), but I couldn't get it to put Vista as one of the startup options. So, I was stuck with a useless, costly, and unreachable Windows partition, and a perfectly working SUSE linux install that I didn't really need, and really only wanted so I could experiment with! Luckily, though, I had my Vista DVD, so I just blanked the whole d**n mess and started over again. It works great now.