Take the hard drive and put it in another computer. Back up your data, then put it back and start over. If you wish to install Linux, make sure your hard drive is partitioned the way you want before reinstalling Windows.
XP didn't seem to have a problem doing what you've done... but Vista might. (I really haven't worked with it enough to be sure).
You could also try a repair install... in fact, probably best to try that first... but still be sure to back up your data. There is no guarantee that the repair install will work.