Help!!!!!!!!!!!!

I know i,m new but i thought you guys could help. I'm good with computers but I have a problem I cant solve alone. My primary gaming computer must be bogged down with viruses and adware but I tried spybot search and destroy, Dr Alex Antispyware, Adaware, and even Norten Antivirus. It always has adware, spyware, And it keeps getting attacked by a trogen back door virus. But whatever i try it always runs slow as heck, and its not that old of a computer. Please Help!!!!!!