Typically that sort of thing is an issue with the DSL service, not something to do with your computer.

I've got a wireless router, and a 2.4GHz cordless phone. Every time the phone rings, it halts my Internet access from the time it starts ringing, to about 5 seconds after the last ring. It's similar to your problem, but has nothing to do with a virus and/or spyware.

Also, just because you have 2Mbps service, doesn't mean you're always going to download at that speed. There are a multitude of reasons why something might be significantly lower. All you have is 2Mbps potential.