|What i would do is:|
Go into safe mode
Click start > run > type msconfig > hit enter
Now from the console that appears select the startup tab, from there deselect everything and restart the machine. What this is basically doing is disabling all applications that start with windows, dont worry this is safe and yiu can always reinstate the applications later, windows will automatically enable those applications it needs to start.
The reason im suggesting this is, if a malicous application is loading with windows it will now be disabled.
However many virus's nowadays cant be stopped this way i usually have to go into the registry to disable them, but thats probably something for later on.
Also check your startup folder, click start > all programs and you should see the folder there is there anything in there?
If you can download the following apps free and install/ update/ run
Spybot search and destroy
Trojan Remover http://www.simplysup.com/tremover/d...
Just google them.
If all else fails i guess a reinstall of windows is required