This is probable a tool that only "expert" computer people will want to use, but I was troubleshooting a couple of PC's which were have some problems, and came across this tool:

It is called Process Explorer

http://www.microsoft.com/technet/sysinternals/ProcessesAndThreads/ProcessExplorer.mspx

Find out everything about what is currently running on your PC. (Like Task Manager - but will tons and tons and tons of information)

It's one of those tools that I'm already saying "How didn't I know about this before"