Winlogon.exe at CPU 99 percent

[paul]

Several times a day my Windows XP machines freeze up and
the WINLOGON.EXE process goes to 99% CPU usage, which slows
down the computer to a crawl. The computers are on a small
network using file sharing. The welcome screen is turned
off, so users have to login using the old Win2K style login
box.

Simple file sharing is turned off as well.

What is causing WINLOGON.EXE to goto 99% and make my
computers useless?

Is it a virus or worm or trojan horse? My virsu scan
software tells me there are no viruses present.

Thanks,
Paul

 

[serge calderara]

Do you have a lot of background programm task whcih start
at the logon phase ?