Ye olde "Windows Explorers is not responding" error

I recently bought a new desktop (Running Vista, and got an upgrade voucher to 7 with it).
But I’m having the annoying “Windows Explorer is not responding” error when I launch several programs.
Like today; I tried opening iTunes, and the error came up. All nice 'n stuff, Windows Explorer came back in less then 2 seconds. However, right-clicking my desktop also made this error appear. I tried using TuneUp Utilities to check for any registry, hard-drive or w/e kind of errors that might be present on my computer.

Googling for an entire day didn’t bring up much, other than a specific scan, which was a command line for the Execute program (something like SFD/ SCANNOW or something… I forgot).

Any idea what can cause and hopefully solve this?
My laptop runs Vista as well, but nothing wrong there.

My desktop specs:
4GB RAM
Intel Quad 2.33Ghz~
Nvidia GeForce NT220
1TB Harddisk space