Need advice on a PC Upgrade

Last week was my Birthday, and thanks to some generous relatives, my tax return, and a tip jar from work, my total in pocket cash is roughly $500.

A year ago, I was lucky enough to win a PC from a College raffle. It's out of date, but I welcomed it warmly. It's a Gateway Pentium II, which I souped up a bit with a DVD Burner, increase in RAM, HD Space, etc.

But I would still like a P3 or P4 upgrade (mostly for the purpose of watching high quality movies and streams without any constant frame skipping). I've heard mention of a PC Tower. Basically, if I understand correctly, it's just the "brain" of the computer, completely stripped from any other necessary factors, like a monitor or any "guts" inside. So I just need to transfer everything from my out of date tower into a newer, more advanced one. And I heard a P3 tower can be found for under $200

However, a Laptop PC would be even greater, being a student and all, and the chance to use it anywhere inside or out.

So, this is where I need your help. A P3 or P4 tower, or a laptop that's under $500? What's the best idea, and what stores can I go to for this? Please, help me out.

I don't think you can get a decent laptop for $500. Then you'd have an alright comp and an alright laptop.

I think all you need is a motherboard that's compatible with a P4, and a P4 itself. Probably some more RAM too. Dunno. I don't feel like looking into it, but be sure everything's compatible before buying anything. ;p

Good desktop computer for less than $500.

Save $400 more and get a good laptop.

You're going to need a new motherboard and processor. Both can be acquired (P4 2.2) for less than 500$ at virtually any outlet imho.

You might need to get different (DDR) ram though. Check into getting a board that supports PC133 ram for the time being.

Going from a MB that supports P2 to one that supports a newer P4 will definately require new RAM.

How's the video on the PC? Is it onboard? If it's an AGP card it's likely to be AGP X1. Is the new MB's AGP slot X1 compatible or is it's video on board?

Will your old power supply be powerful enough to run all your new components?

Will you have enough cooling for the new stuff?

Do you have the necessary equipment to properly static-ground yourself before overhauling your rig? (hate to see you short something out and have to spend more money).

What OS will you be working with and, while it's highly unlikely that it won't, will it accept and run some of the older components you'll be salvaging from the old rig?

Perhaps most importantly, since you're using a proprietary PC, download Belarc Advisor (it's free), run it, and take a look at how many of your installed physical components come up saying "Gateway" next to them. Do you know where to get the appropriate drivers for those intalled components for whatever operating system you install on your new rig? (should look into it anyway, it's always good to have access to your drivers even offline ;) ).