I'm not sure that your problem is something nasty running on your machine - if there is something running it's using very little of your processor's power, as according to the screenshot 'System Idle Process' is using 99% of the processor. ('System Idle Process' is virtually a dummy, it soaks up the processor's unused clock cycles when it's not doing very much.) There are six unknown services running (they're hiding under the name 'svchost.exe') so it could be one of those, there's also some sort of Google Updater which might be generating a lot of traffic (I don't know what it does, so I don't know whether it might be uploading or downloading).
Is there much sign of disk activity - clicking noises from inside the case or the disk activity light being on a lot of the time? Your disk drive might be in a bit of a mess which could lead to Windows having to go hunting for things every time it needs them instead of being able to go straight to them. Try running Chkdsk and Defrag (in that order) and see if that speeds things up at all.
There's a useful tool called HijackThis, which will scan your computer and generate a report of all sorts of things - running processes, programs launched at startup, etc etc. It's available from
http://www.spywarewarrior.com/uiuc/merijn/HijackThis.exe or
http://spywarewarrior.com/files/HijackThis.exe If you want any help deciphering the report you could post it here, (you can save it as a text file and paste the text in), there's also a very good site called Spyware Warrior (
http://www.spywarewarrior.com/) where volunteers will help you to rid yourself of spyware and other nasties. The main tool they use to see what you've got is HijackThis, so you'll need that anyway so you can post the results to their board. I've used HijackThis, it's safe, and I've used the services of Spyware Warrior to get something horrible off my computer and they're pretty good. (Usual disclaimer applies though - use at your own risk, not my responsibility if your computer packs up, etc etc.)
Hope this helps!
