I know I have been roughly here before, but not with these same questions.

Our PC is a good spec, but seems to be running slowly these days. I do very regular maintenance (Disk Cleanup/Defrag, manually file maintenance, Ad-aware, AVG etc etc), but it still doesn't seem to perform how I think it should.

It's a Pentium 4 3.0ghz processor with 1.0gb RAM. I have suspected the hard-drive for a while, but it does work and never errors. When it had a go-slow moment, which it often does, you can hear the HD or something in the PC working hard.

My question is this, is it possible to conclusively prove whether this is a HD problem or a RAM problem? Does RAM go faulty? It's a Western Digital HD and I have run WD's Diagnostic program and it all tests OK on that. It's a 200gb drive and has 150gb free, as I have a second 500gb drive for data storage, so it's not even like its full!!

I don't really want to throw parts at it needlessly.