Recomand a MoBo and chip

That'a very good value, and it will provide good performance.  For best results, you should use PC3200 RAM to make use of the fast memory controller.

Love all the  Gigabyte MoBo's,  I've built 8 computers this year and all with Gigabyte mobos.  Easy to setup... decent instructions... and VERY dependable.  I agree with Callandor... don't  cut corners on memory....

A couple other things you will need where the system is an oem system is a caes (most likely the retail atx motherboard will not fit in the hp case) and a power supply (most oem manufactures like hp and dell use proprietary power supplys that may plug into a retail board but can cause damage).

HP uses standard ATX plugs, but motherboard may not be standard uATX depending on model.  Also power supply may be SFX or uATX instead of standard ATX.  Either way, you will need to upgrade power supply if you haven't already done so.

It's probably a recent enough HP Pavilion to have a standard uATX motherboard.  Power supply could be any one of 3 different form factors.

The motherboard you selected is a full ATX motherboard and I don't believe it will fit your case.  Since you will need to replace power supply anyway, purchase an inexpensive, decent quality case that comes with a power supply.

Also, have you considered that you will need an AGP 8X/4X video card if you don't already have one.

Here's a mobo that will probably fit your case:

http://www.newegg.com/Product/Product.asp?Item=N82E16813138264

Or a case if you wish to go full ATX:

http://www.directron.com/c583ti3bbfu2ad.html

Thanks Willcomp.

I already have a nice AGP nvidia card which did not come with the HP and a new 350 power. I'm thinking of purchasing these parts:
case:
http://www.newegg.com/Product/Product.asp?Item=N82E16811119075

Motherboard:
http://www.newegg.com/Product/Product.asp?Item=N82E16813128307 

chip:
http://www.newegg.com/Product/Product.asp?Item=N82E16819103535 

Any feed back ? ? ?

Good combination.  

I have a Cavalier case and really like it.  Roomy and quiet, easy to work in.  It's rather deep though (front to rear), so ensure you have sufficient space.  Height and width are about average for a mid-tower case.

I haven't used any ULi chipset mobos.  Old Acer Labs (ALI) by another name if I remember correctly.  Should be OK.

I primarily use Gigabye motherboards and have had very good success with them.

The Athlon 64 3200+ is a very good CPU.  

The Cavalier case I mentioned contains a Socket 754 Athlon 64 3200+ on a Gigabyte K8NS Pro mobo.

Thanks Willcomp,

Couple more questions:
I thinking of purchasing this memory:
http://www.newegg.com/Product/Product.asp?Item=N82E16820145440

as for cooling my chip would you have any suggetions?