My laptop is torturing me to death

I've posted this in software too, I've been advised it could either be software or hardware issues:

Hello - a kindly and learned gentleman has been helping me out on the Malware forums, but it seems my laptop's torturing symptoms are unrelated to that, we've been through everything.

It's an Advent 6651 Pentium T3400 2.1GHZ, Windows Vista Home Premium

Basically the issue is that if I watch or listen to anything - net streaming, dvd, vlc, wmp youtube etc etc, its violently interrupted and distorted. It often is accompanied by a CPU spike to 100 percent in task manager. Also, unresponsive mouse clicker a lot when doing anything, as well as not respondings and general jammy sloth. It's been going on for months. I've tried updating video card drivers, virus scanners etc etc and can't find a cure. I've never faced anything so irritating.

If anyone could help me I'd be so grateful.

This isn't just the above things, the laptop does it sometimes even with the startup windows noise, or my Avast audio alerts.