First off, Hello everyone! just joined!
OK, hope this doesn't get too confusing.

I bought my PC at a local PC store (not a brand name)about 4 years ago, and it runs beautifully albeit a bit slow. specs are: AMD athlon XP 2000+ clocking 1.666 mhz. on an MSI MS6561 745 Ultra MOBO. I have 1024Mb RAM. Radeon 9200SE Video Card

OK I just bought from a friend his old Gateway PC with a bad HD for $100. I replaced the HD with one I had laying around and got it back up and running, it has an Intel Pentium 4 2.4 (I believe) CPU in it.I think it is an Essex Nina MOBO too. Can I take the chip out of it and put on my MOBO to speed mine up a bit? I understand that I'd have to make some changes to the BIOS, which I'd have to come here for help with.

Again, I hope this wan't too confusing!
Thanks in advance!

Welcome to the Forums.
Do you mean change the processor from the Athlon xp to the P4? or the whole board and processor?

Sorry, didn't clarify there. I just want to put the Pentium 4 chip on my motherboard . My AMD only clocks 1.666 Mhz. and the Pentium actually clocks at 2.4. Basically, I just want to swap chips. Additionally, the Gateway is one of those flat type of towers, I don't know what you call them! LOL...the monitor sits on top of it...it takes half height video cards and stuff. I'd like to build it into a second PC for the kids. I have some spare parts, and a Radeon 8500 Video card, but it wont fit in there (too tall) can I buy a mid tower and transfer all the parts?

Thanks for responding so quickly.

Well sadly you cant.They use differnt software and different sockets.You cant even get a better processor at stores.Their are few sellers.You can get a celeron and a motherboard for $50.00

Well, that just figures. I have three memory slots in my MOBO, with one 512MB stick and two 256MB sticks. crucial.com says it'll take three 1GB sticks. I'll go that route first. That should help some. It keeps telling me I have 1024 Total but only 670 available.

What about putting all the Gateway stuff into a Mid Tower? Can I disable the integrated graphics on it, and install my old Radeon 8500?

Well if i know the motherboard model or have a picture of the expansion slots i can tell you
But the card is agp and aslong as you have an agp 2x or 4x not sure of 8 it will work.

If your old PC was custom built by the computer store, which I assume it is by the fact that it doesn't have a brand, it may be able to get a more powerful processor for that socket (though RAM is a good first choice). If you know your Motherboard's brand and model number, I could tell you. If you don't know it, I believe I can tell you how to find out.