http://www.whatsrunning.net/
Great piece of utility program for Windows 2000, XP and 2003.
It not only shows what's running in your PC, it also has lots of
other information. 
Take for example a legitimate Windows process, winlogon.exe
It shows you the File Version. The File Version is useful in
telling whether that program running is legitimate.
In my case, it shows it's by Microsoft, so I can be assured that
it's safe. No malware. 
It also shows the modules loaded (not really important to an
average user, unless you want to know what's happening to your
PC).
The Services tab shows what services are running on your PC. Not
too much of a concern for an average user again.
IP Connections tab shows all the connections that are opened,
listening or awaiting closing. Much better than a firewall log. But
it doesn't protect you from anything. Very useful when your Net
surfing speeds slow down a lot and you want to find out what's
happening.
Drivers tab shows the drivers installed on your PC. Don't think
that you have so few devices, you will have few drivers. You will
be surprised!
Startup tab shows the programs that start when Windows starts. You
can disable and enable them via here, without ever messing with
msconfig. Useful for a newbie. 
System info tab basically shows your system specs, but not in much
details. It's better to use Belarc Advisor or CPU-Z for a much more
detailed system specifications. 