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.
Yesterday evening I started noticing that MSN Messenger, AIM and mIRC kept getting disconnected for a short while (~5 seconds) and then they reconnect. I have performed anti Virus and Spyware scans but they've come up blank. Also my internet connection is slow at times but I am able to download ~50k/ sec. My ISP is Tiscali and I am using the 2mb package. I am connecting via network cable to a router.
Task manager is running the following programs :
System Idle Process