Overinstallation can solve the problem and you won’t lose your programs, settings, data, files, etc. Just choose ‘Repair’ installation of Windows and install ‘over’ the old installation.
http://support.microsoft.com/default.aspx?scid=kb;EN-US;315341
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q314058
http://www.webtree.ca/windowsxp/repair_xp.htm
You will still have all your data.