Malwarebytes

http://www.youtube.com/watch?v=VpyoY7MT8xY

Free to use,

And works on all windows ver.

Check it out if you think you have a virus or a trojan.
And if you do not think you have one, Try it anyways just to make sure.
Description of Malware
AdwareAdware (or spyware) is a small program that is designed to show advertisements (in various form and degrees of intrusiveness) on your computer. It often reports personal information back to its owners. As a result your sense of privacy can be violated.
BackdoorA backdoor is a small malicious program that is used to gain access to a computer by bypassing the computer access security mechanisms. It gives the attacker almost unlimited rights. While it can be used to spy on a user, it is mainly used to install other malware on the system.
HeuristicA technique designed to detect malware by empirical means but without having the specific data.
MalwareA generic name for all types of malicious programs: adware, backdoors, rogues, trojans, viruses and worms.
RogueA rogue program is a malicious program that is disguised, for instance, as trustworthy anti-spyware programs or registry cleaners. But these programs are only put on the market to scare you into buying these programs because they make exaggerated claims about the safety of your computer or, worse still, give erroneous scan results or put their own malware in your system.
TrojanA trojan (or Trojan horse) is a small malicious program that pretends to have a particular function, but that only shows its real purpose after execution and that purpose is often destructive. Trojans cannot multiply themselves, which differentiates them from viruses and worms.
VirusA virus is a small malicious program that multiplies and is capable to attach itself to other programs after being executed. It then causes an infection and causes various degrees of damage to your computer.
WormA worm is often characterized as a malicious application that will use a host machine to infect other machines. Therefore worms can create enormous damage on networks with multiple computers.