Virus / Spyware disallows connection?

I have a v/sw type trojan that is corrupting my Google uses and redirecting me to BS ad sites. It will not allow ANY of my Spybot detection to work AND I've recently found it has taken away the ability for any program i use, that requires a server link, to operate... It infrequently refreshes my Internet Gateway to the point of complete shutdown... Task Manager shows an inflation of Mem Usage for various Processes. I've DL'd plenty of propietary virus software but nothing functions. Where can i go within my PC to manualy disable/destroy it?