your not on a dell are you

No. I have a Gateway.

Run a virus scan.

There is a worm which blocks access to Windows Update, and it is really easy to test.

Can you see all six images on the “Conficker Eye Chart”
http://www.confickerworkinggroup.org/infection_test/cfeyechart.html

@jaytkay the penguin is cute, but i really like the puffer fish

It might be a virus. Do you have a ant-virus program? If not use AVG the free version.
And you might also maybe* have deleted some files which links to the Windows Update.
and it depends on wich OS you use?

I have Vista. I will try some of your solutions this weekend. thanks

Run both a virus scan (Avira or Microsoft Security Essentials recommended) and Malwarebytes anti-malware. They catch different things.

http://www.microsoft.com/security_essentials/

http://www.free-av.de/en/trialpay_download/1/avira_antivir_personal__free_antivirus.html

http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html

But a MAC and forget about viruses and error messages