There's a handy little bit of free-ware available from the PCMagazine site called end-it-all. It is a little more useful than Win98's ctrl-alt-delete. Gives you a good idea of what's running in the background on your system, and allows you to close or kill most of them.
Go here for the end-it-all it:http://www.pcmag.com/category2/0,4148,23,00.asp
Click on the utilities from A to Z link. Lots of useful stuff there, by the way.
You may have to register for the download. If so you'll have the option of subscribing to a few newsletters. Probably the only one you'll want is the daily usertips, if you want any at all.
I'd also recommend scanning your system immediately.