boot from the windows XP setup disk, find the recovery console, login in to the last version of windows usually C:\windows , navigate the disk to a placve where you know are some giant files you can recover and delete them
it sounds complicated but its not, just follow the instructions, the only complicated part is finding the data you can delete that will give you enough space, you may get away with just deleting the pagefile.sys which is usually at c:\pagefile.sys
http://support.microsoft.com/default...NoWebContent=1
After thats done, rerun the installer from the XP CD. you may even get away with a recovery step from the boot CD instead of a reinstall.
Free up as much space as you possibly can without deleting stuff you need.
if you get stuck come back and get some more clarifications, if you can use dos you can use the recovery console.