In order to remove any type of malicious infection, you need to know the reason behind its occurrence. There are different removal steps for different types of virus/malware/Trojans. First of all identify the kind of infection your computer is having. Secondly, remove recent downloads/installations which triggered the infection. Thirdly, clean registry/cache/temp files/junk items off your system. And last but not the least, perform advance system scan with some strong antivirus application and quarantine detected threats. You may choose Immunet (http://www.immunet.com/), Norton (http://us.norton.com/), Bitdefender (http://www.bitdefender.com/), Kaspersky (http://www.kaspersky.com/), Malwarebytes (http://www.malwarebytes.org/) etc. Hope this helps.