Hi isildur,

Not sure about what backups you have, but doing a format and reinstalling windows is always an option.
It probably isn't.................... if he has done the tests I suggested, then it is only a Yahoo! problem, and Windows is working OK?

i_m_DuM_aaAAs$$s!#

Can you use another computer and try to get into your Yahoo! account. If it is not your computer then be sure to clear cookies and history and log off afterwards

Were there any messages in your log files?

Go into "setup" and turn off the reboot on error options............. that might get you a blue screen with an error message........... please let us know what that says, particularly the sets of numbers and letters