it is quite likely that the machine has got the recovery / restore mode switched on.
In safe mode go through to tyhe control panel and look for admin tools or just do a seartch for 'restore' and then you should be able to put the machine backl to the last time it wirked.

if not on using safe mode boot there is an option to go to the last good working version, try that
M

Hi,
it sounds like you were surfing the net without a anti virus program running, as you said you downloaded one after downloading a lot of other stuff. You probably have a lot more viruses hiding in there.
You need to check deeper for viruses and malware. Go to:-
http://housecall.trendmicro.com/
or:-
http://security.symantec.com/sscv6/WelcomePage.asp
Download and run to remove any viruses you may have. (Sometimes a virus will stop you accessing an anti-virus site, so try going through safe mode (Tap F8 on boot up) and see if you can access it there.)
Then go to :-
http://www.malwarebytes.org/
or;-
http://majorgeeks.com
Download, then run a “quick check” your PC for any problems, if still there do a “full scan.”
Never go on-line without your virus protection and your firewall running.