Upgrading ati 3200 onboard

I an using an HP a6750f pc, with an AMD Phenom x4 (9650 Quad-core) proceesor, ATI Radeon HD 3200 graphics. I have 8 mb ram, a 64 bit system running vista home premium. 750 gb hd and want to upgrade this integrated graphics card. Is is possible and if so can someone point me in the direction of how it's done. This is supposedly a gaming system ( fat chance) but the video sucks. Is it possible to disable the on board card and replace it . Any suggestions for the card to purchase as a replacement. I am willing to spend $200-350 for the graphics card. But don't know yet how to disable the on board and enable a new card.

I am a novice, learning how to work with hardware and replacements, this is the 1st time I have ever needed a new graphics card. I've replaced hd's, fan's, controllers, memory, but this is my first system with an on board graphics card. Currently the onboard card has 256mb of ram, I like a card that will allow an increase of ram to at least 4mb. I want to do video, photos, tele-conferencing (good quality) and really don't have an idea of what I should be contemplating as a purchase.

Thank you all so much for being here and in advance, I thank you for your suggestions and advice.

athene

The onboard chip itself cannot be upgraded (it is part of the chipset on the MB) however it certainly can be disabled and replaced with a discrete card. Two major questions though:

1.) Do you have at least 1 free PCI-E x16 slot?

2.) What is your power supply and what connectors does it have? The stock PS is probably pretty weak and will limit you too much, so you may want to include a PSU upgrade ($50-75) in your budget as well.