If you are trying to install the same version of XP on top of what you installed previously, you don't have to.
You can simply change the Volume Licensing product key and continue use.
However you must use a Retail Key with a Retail disc, OEM Key with an OEM disc, etc.
There are a couple of Windows XP CD Key Changers floating around that can automate this process for you.
If the XP version numbers are different then and Upgrade Install (which you attempted) will not work in your case so you might want to try to set your system to boot from the CD-ROM and wipe the hard drive clean by formatting it, then install the proper disc on it.
Windows Reinstall.com has set by set instructions with pictures depending on what you want to do. Just choose your Operating System and follow the appropriate instructions.