logging on then instantly logging off

[Richard Wells]

When I try to log on to any profile, it try's to log on then for a brief
second you see background then you see logging off and back to pick a
profile to log in.

 

[Rock]

When I try to log on to any profile, it try's to log on then for a brief
second you see background then you see logging off and back to pick a
profile to log in.

Have you recently removed any malware? This can be an artifact of that.
See this link:

Unable to Log On To Windows XP After Removing wsaupdater.exe
http://www.lavasofthelp.com/articles/v6/04/06/0901.html

You cannot log on to Windows XP after you remove Wsaupdater.exe
http://support.microsoft.com/kb/892893/en-us

If that doesn't help see this:
A User Logon Request Is Rejected Without Any Messages
http://support.microsoft.com/?id=313322

 

[Pegasus \(MVP\)]

When I try to log on to any profile, it try's to log on then for a brief
second you see background then you see logging off and back to pick a
profile to log in.

This happens when the file userinit.exe is missing, e.g. because
of malware (as suggested by Rock) or because of a changed
system drive letter. The cure depends on your setup, i.e. if the
machine is networked or if you have ready access to another
WinXP/2000 PC.