Does this problem also appear when you reboot in safe mode
using the <F8> method ?How to start Windows in Safe Mode
If still no logon in your account possible, can you logon as administrator
is safe mode?
If you can login that way, try using the windows xp cdrom: put it in and go to start > run > type sfc /scannow
. The system files on the computer are getting compared with the original on the CDrom, is promted something is corrupted , click yes to let it repair.Description of Windows XP and Windows Server 2003 System File Checker
Or try using system restore
(it's an options you get at one point, while starting in safe mode )
Or does, in the menu with safe mode, safe mode with networking,.. the option "last good known configuration" helps to solve this issue ?
Did you removed a virus or other malware (f.e. Blazefind) before this occured ?Logon - Logoff loop, also caused by BlazeFind
(in the middle of the page)
Are you an 'restricted user' (no admin account) ? Perhaps this article might be usefull then:A User Logon Request Is Rejected Without Any Messages
Good luck !