Will this: http://www.compusa.com/products/product_info.asp?product_code=310619&pfp=BROWSE motherboard fit in my computer? Will all my internal hardware work with it? I have an hp Pavilion 503n with an intel 845GL chipset. Everything is always funny at first, until someone gets hurt, and then it's just hilarious!

Without tracking down the info for your computer and following the link, I will pass on the basics. The "form factor" is what determines the compatibilty of cases and motherboards. Most are "ATX" form factor. If you have an ATX case, you can fit in any ATX motherboard. Best Wishes, Bob

I'm not sure if the Pavilion's PSU is proprietary or not...if it is, it will have to be replaced too

What are you gaining by the swap? Do you really feel that a VIA chipset with integrated video is better than an Intel chipset with integrated video? There is one other point you should be aware of. Sometimes large manufacturers like HP, Dell, etc. use OEM motherboards from the likes of Intel and they are just slightly different, and standard motherboards like the one you reference just may not fit the case exactly even though it's an ATX specification.

Of course that board would fit. it is a Micro ATX you can't get smaller. But I know you would get better performance if you got an AMD ANTLON BOARD AND CHIP.

I Would like to swap because this board has an AGP slot. Everything is always funny at first, until someone gets hurt, and then it's just hilarious!

Maybe not nowadays, but when my parents had an HP (MMX micro) and their PS went, I had to replace it with an HP supply. Why? Because it's proprietary to HP motherboards ONLY!!!!! Which means it will not work on other mobos. Again, this was on an older computer, but I would tend to think they are still that way (so they can make money on you when it breaks). If it ain't broke upgrade it!!!