Ubuntu :: Noob With A Freezing Netbook?

I have a Dell Mini Netbook, running Ubuntu 8.04 - "The Hardy Heron". Other than Skype and Chrome, I don't have any programs on my netbook that I didn't get from the "Add/Remove" program.For a long time now, I have been having an issue with my netbook where after being on for about 5 minutes, sometimes as long as 10 minutes, the system will star to freeze up, to the point where nothing works, not even the mouse. I know it's freezing and not locking because you can move the mouse a little bit, but it is too slow to be able to do anything, and normal processes that take seconds normally, will take upwards of 5 minutes. At least.

At one point I found and ran the Ubuntu-version of Task Manager, System Monitor. I sat and watched it for the 5 minutes it took for the freeze up started happening. RIGHT as the system froze up, both of the CPU's and the RAM maxed out at the same time.At this point, I would normally just go into Task Manager and see what shouldn't be running, and end whatever I see that I don't like, and then go delete the files for that program(s). Or at the very least, just system restore (because I ALWAYS have backups off the computer). But I don't know how to do any of that on Ubuntu.The netbook ran fine for almost 1 1/2years before this started happening, and at first it wasn't an issue that happened all the time. It happened every now and then, but restarting the netbook would fix it for a few days. And it slowly became an every week thing, then every day, and now every time the netbook turns on... which kinda sounds like a hardware issue, because software shouldn't change over time if there is no change put into it.

By the way, at the very least I'd like to know if there's a way to totally wipe and re-install my netbook from scratch. I don't need any of the files on it, so that's not an issue. Also I've heard that I might actually want to be using Xubuntu of I'm having a memory issue, so is there a way to replace Ubuntu altogether with this Xubuntu?