i have an hp 526x. the motherboard is an asus 478 socket. can i replace this with any 478 socket moterboard or

http://h10025.www1.hp.com/ewfrf/wc/document?docnam...

That's your motherboard in micro ATX form factor. You can not use the larger motherboards in ATX form factor.

If you are planning a motherboard replacement, better move up to current formats like LGA775. Socket 478 format is outdated and slow. Consider the cheap Intel E2140 or E2160 paired with any of these motherboards:

http://usa.asus.com/products.aspx?l1=3&l2=11&l3=18...

http://usa.asus.com/products.aspx?l1=3&l2=11&l3=49...

http://www.asus.com/products.aspx?l1=3&l2=11&l3=18...

The important factor is space in your case. I expect it will be a standard size ATX board in which case it doesn't matter what you replace the board with.

If you were only replacing the processor then the socket is the all important factor, but to replace the entire motherboard your only considerations should be size of new board and connectors for your drives. So if you have SATA HDD don't purchase an IDE only.

Yes you can replace it with any other intel 478 motherboard as long as it will fit in your chassis. Hmmm i wonder if they still make them.

IF it can run at the specified FSB(or more) of your proccessor.