Check out newegg, they have the best prices and very fast shipping.. Products are reliable too. I don't think it really matters what type of mobo or processor you get.. However, I prefer amd over intel. ASUS motherboards are reliable.. Make sure the processor socket and ram matches.. you can usually check your CPU cooler's manufacturer and check what cpus you can adequately cool.

I just built a cheap box to run Vista on a couple weeks ago. I was on a tight budget so I stuck with a AMD Athlon64 X2 3800+, 2GB of RAM, and an ASUS M2NPV-VM motherboard. Don't know how the mobo shapes up on reviews, but it's working just fine. I've even got mine just using shared memory for video, which saves the cost of a graphics card, and the mobo has 2 IDE buses and 4 SATA ports. It's also got an AM2 socket, so there's room can upgrade the processor later if you feel like it, and a PCI-E x16 if you want to throw a GPU in. I put a 400W power supply in, just to be on the save side. For the case, PSU, mobo, CPU, and RAM I spent under $500, and carried over two HDDs and a DVD-burner from another computer.

If you're not concerned with cost, look into getting an Intel Core 2 Duo, but I've not looked into parts for those at all (like I said, I was on a budget).

As to CPU cooling, you'll want to use whatever comes with your new processor. Usually different sockets have the fan mount differently, and most processors come with the proper fan, so why not use the proper piece?

Sounds like a decent build, what did you pay for that? I just upgraded my processor to a 4400+ 2.64 ghz and 2 gigs of ram, and it was about $200

My total was right about $450

wow, thats a pretty good value.. something like his build would be great for you

Buy the CPU as a boxed and it comes with the cooling fan.A post Josh made about AMD's the newer ones run alot cooler than a P4.All the Hardware you mentioned you will be able to reuse without buying that.you can even get a new case with power supply real reasonable.What ever motherboard you go with make sure it will fit that pavilion case.but you would be better off buying a new case also you can get one with a 430 watt power supply pretty cheap at new egg.that HP propably has a 190 watt.

All sounds great. Here is what I'm looking at, at Newegg.
Case: Apevia w\500w psu micro ATX price 98$
mobo: Intel micro atx Bkdq965gfekr lga775 intel q965 express, it's sata and ide so I can use the cd\dvd burner and floppy disc drive and my newly purchased sata hdd.
memery: Patriot extreme perfprmance 2gb 240 pin ddr2 sdram dde2 800 (pc2 6400)
Processor: Pentium 4 cedar mill 3.2 ghz lga775 em64t
The mobo is 119$ ,memery will cost 89$ after rebates and the processor is 77$. with an extended warranty on processor and mobo all came to 450$ plus shipping.
Could have went with one of Apevia's 420w case but then I saw the 500w one for about 20$ more so why not get the bigger psu. It won't pull any more current than it needs to and I would have power to spare for up grades later.
The reason I went with a pentium processor is that every computer I've had in the past had intel inside and they all gave great service.
We started out with a Tandy and dos, when windows 95 came out, we got a Micron and when the Hdd ch\rashed on that one after about 4yrs, we ordered another Micron w\98 on it, the next one was this HP because micron had stoped making pcs and had went to sotfware only for business'. This HP lasted about 2 yrs before it started giving us heartburn, so we replaced it with a Gateway. This HP sat in the closet for about 2yrs,and after I retired I got it out and started messing with it, did a recovery and got it up and running for about a year when the Hdd crashed and burned. Now I find out that the intel 82801 chip has crashed and there is no help for it that I can find. No one wants to sell just a tower and they are all coming with Vista on them and from what I have read I don't Vista just yet. When Bill Gates says that Vista isn't for everyone it makes you wonder about it.
Looks like AMD has a lot of fans here.I thank all who responed to this thread for your opinions, I asked and I got. Thank you all.

Great. Sounds like an awesome build.. enjoy.

I'm not a fan at all of Pentium 4 chips. They had high clock speeds but relatively poor performance and high energy usage. Get a newer chip, and one with 2 cores. An Athlon X2 3800+ is also about $75 on newegg and you can find a comparable motherboard to fit it.