Event Viewer will often give a clue to what has been happening with the
system. You highlight Application or System in the left pane and entries
will appear in the right pane. If there are red or yellow warnings, you
double-click on one to see what it is. While it might not be clear to you,
the error can then be Googled or posted back here for more help.
Since the problem seems to have disappeared, you can stop worrying about it.
If it comes back or for future problems of a like nature, here is the normal
troubleshooting path:
The First Question Of Troubleshooting: If the problem is new, what changed
between the time things worked and the time they didn't?
The Second Question of Windows Troubleshooting: what is the malware/virus
status of the machine? If you think it is clean, what programs (and
versions) did you use to determine this?
Be sure the computer is clean:
http://www.elephantboycomputers.com/page2.html#Removing_Malware
If you can't immediately answer The First Question and solve the problem
that way, then go through the steps at the link to answer The Second
Question. For a preliminary answer you might want to skip running Multi-AV
if you have a good antivirus installed already, but don't skip the
maintenance preparation and scanning with Malwarebytes' Anti-Malware (MBAM).
If the computer is completely virus/malware-free and running MBAM didn't
solve the issue, do clean-boot troubleshooting to find out what is running at
Startup.
How to troubleshoot a problem by performing a clean boot in Windows Vista -
http://support.microsoft.com/default.aspx?scid=kb;EN-US;929135
The free Autoruns program is very useful for managing your Startup -
http://www.microsoft.com/technet/sysinternals/default.mspx
The "Reply to Newsgroup" is part of Mr. Foldes' signature and not part of
his answer to you. It means in effect, "don't send me a personal email -
reply to the newsgroup instead".
Malke