1. bofore unistall, please a bootable windows xp cd.
2. restart and boot into windows xp cd
3. choose 1st repair option
4. in command line, type fixmbr
5. restart back to windows xp
6. right click my computer->manage->storage management
7. Remove your unrecognize partition (which is linux OS partition and swap)
Backup everything to avoid anything goes wrong.