Windows XP's logonui.exe error?

Disable all services in your computer, try to change to the clic windows theme and restart the computer. that will surely work. Also try some free computer malware clearing tools, check here a href="http://www.bytechip.com/2009/11/pc-fix1/" rel="nofollow"http://www.bytechip.com/2009/11/pc-fix1//a