there are less processes running, which would include the viral process if there is one, allowing the virus scan to detect more easily, because the viral process could be stopping your anti-virus software from doing its job. But your computer seems to have a Virus or adware/spyware, which are all reasonably easy to move. Ad-Aware SE and Spybot are exellent adware/spyware removals. Norton is a top of the line Anti-Virus remover. Also run an online virus scan from here --->
http://security.symantec.com/sscv6/home.asp?langi...SYGRHYTINMHDKDCWLL <--- if this doesnt work contact me, and will try to help you further. Goodluck, hope it all works out for you