Svchost (or taskhost) is a helper process for running a number of other applications. It may be running good stuff or bad stuff.
You can plug a process name into Google and find out what it is. Most sites that will tell you will ALSO want to run a "scan" on your machine. It's not a good idea to let them do so.
Programs like Ad-Aware and Spybot will detect non-viral things you don't want. Spybot will also help you control start-ups and processes under its TOOLS section if you don't know, independently, about those things.
In general, browser bars, shopping buddies, stuff like that are undesirable; many will hijack your browser. IE, in particular, is bad about accumulating a bunch of that stuff.