I'd like to keep windows xp on since I know it works. I'd hate to wipe that off just to get a new operating system on there and risk that one not working. And I don't have a windows cd to put it back on.
First of all, make an image file of your Windows XP drive *immediately* if you want to keep it. A hard drive can fail at any time. Since you have no disk to restore your Windows, what would you do if your drive suddenly failed--and this has nothing to do with Linux? If your hard drive is a Seagate, Maxtor, or Western Digital, you can download a free version of Acronis TrueImage that will make an image file of your hard drive.
Do you have unformatted space on your drive? If you don't, you can shrink your XP partitions losslessly with a Windows tool like Partition Commander. I think GParted, which comes on some VL CDs, will shrink a Windows partition losslessly, but be sure to confirm this first.
But to go back to my first point, ANYTHING and EVERYTHING you don't want to lose *must* be backed up all the time.