i am wanting to add a video card to my A1510N. Motherboard manufacturer's
name: Asus A8N-LA HP/Compaq name: Nagami2-GL8E i upgraded the OS from vista
to XP Pro. i have a couple of question that i hope someone can answer for
me. can i turn off the onboard video and return the shared resources to
mobo? what is the best card i can upgrade to with PCI Express X16 that the
computer accomodates?

Thanks

Much will depend on what power supply your system has and if you're also going to upgrade it. With the stock power supply you're probably looking at a card such as a Nvidia 8600 GT DDR3 or an ATI 2600 XT. If you add a power supply then almost any PCIeX16 1.0 or 2.0 card would work......as long as it fits in your case. The onboard video will shut off when you put a graphic card in PCIex16 socket. You might have to measure how much room there is at the socket to see what will fit.

all the documentation i have seen says vista. i have upgraded from vista to XPpro. is that going to be a problem?. if i had a huge power supply what would be the susgested board to use? will the performance difference be worth putting a larger power supply in my computer?

thanks for the insight....

Yes, almost any PCIe card can beat to dust an onboard graphics solution. That's talking low-mid and up (GF7K and HD2K series).

Now, the PSU thingy: from what i found, looks like you have a 300W PSU, with doesn't cut it. Get a 400W+ PSU and upgrade to a 9600GT or a 3850 IMO (or anything on that price range). That would give you a HUGE boost.

Also, disable the onboard video once you get the card installed on your PCIe. If you don't do that, u'll be running with 2 video cards and i'm guessing u don't want that.

Esop!

Just to clarify some of the good advice here...
Some boards will automatically disable on-board video, some you need to go into the BIOS and turn it off. Check inside your BIOS and your manual for any instructions or settings for the on-board video, and just before you physically install your new Graphic Card, turn your on-board off if there is an option to disable. Most boards with on-board video can be switched off in the BIOS somewhere, even if it auto-detects your new card and uses it fine on installation.
You will need a better power supply for you new video card.
Also, you said you upgraded from Vista to XP-Pro?
That wouldn't be an upgrade, that would be a downgrade?!?
Do you mean that you upgraded from XP-Pro to Vista?

A 300W PSU is sufficient for an 8600GT or 2600XT; neither requires an additional PCI-E power connector. What games do you want to play, and what is your budget?
Vista to XP-Pro is, at worst, a lateral move. If it was Vista Basic, then it's probably an upgrade based on features. If your PC has no more than 1GB of RAM, it is also an upgrade for performance reasons. Apparently, enough driver issues and bugs in Vista have been squished that if you have 4GB or more, then it may have made no notable performance difference.