Hi,

 

I think the first thing to do is check for virus/other malware

If you can get IE to work run these online scans. 
Let them fix anything they find, but take a note of the names of the nasties in case they are needed later

 

Panda            http://www.pandasoftware.com/activescan/com/activescan_principal.htm

 

Trojan Scan  http://www.windowsecurity.com/trojanscan/

 

If not fixed download and run

Microsoft Windows Antispyware
http://www.microsoft.com/athome/security/spyware/software/default.mspx