you may need to do repair install of XP. it will restore all the system files and leave your data and settings intact. You will need windows XP installation disk put it in disk drive and boot from it. Boot from CD - How to Boot your Computer from a Bootable CD
once you know how to boot from bootable installation disk. put the disk in drive and restart the computer. follow the steps given in this article for repair install How to Perform a Windows XP Repair Install
XP disc download from http://tinyurl.com/5box53
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