Bizarre Noise

This is weird. I was watching a video clip on YouTube. All of a sudden, The Monitor went dark, the PC locked up and there was a noise that sounded like a noisy rattling washing machine (or something) It seemed to be coming out of the speakers.
I did a hard shutdown and restarted with no problem and nothing in the event logs!
Anyone ever run into this? I've never heard anything like it.
Thanks

I have a older Dell Dimension 4500
XP Pro w/all upates
2.00 gigahertz Intel Pentium 4
512 MB memory
8 kilobyte primary memory cache
512 kilobyte secondary memory cache
NVIDIA GeForce4 MX 420 [Display adapter]
Creative SB Live! Value (WDM)

 

No, I don't use aim. Thanks for the reply.

 

Well I had time to sit down and take a look at the problem. It appears to be the video clip. I went back on YouTube and watched several different clips. As soon as I went to the clip that was running during the problem. The same thing happened. At least it's not my system.
Thanks!