My six year old PC would like to laugh at this point... ok, so it doesn't do games, but then again neither do I.. I do on the other comp
I thought ctrl + alt + del was the way to find out how much power (assuming you mean CPU) you're using...?
Progs vary... so, your cpu usage will go up and down....
How much memory do you have? more ram is better than a little... I've got 384Mb of ram in this comp and it takes a fair whack before it starts crawling............ (700mhz celeron processor)
And most modern computers tend to go a little bit mental when they're overheated for whatever reason... but, if you look after stuff, it lasts a bit longer.
Depends on your specifications too.. generally, you don't need an external application to tell you about your pc.. just ctrl + alt + del = there's a couple of screens, one of them tells you how much CPU you're using...
and from start, you can stop some apps running by typing in 'msconfig' and if you want to know your specs, type in 'dxdiag'