|"....I then boot into Vista and it also uses the Radeon 7000 even though it is disabed in the device manager...."|
There are no Vista drivers for the Radeon 7000 chipset. Vista is using default video drivers.
In most cases, if the Radeon 7000 card is AGP, the mboard's onboard video is automatically disabled when you install an AGP card in the AGP slot, and the settings regarding the amount of ram shared with the onboard video in the bios Setup are ignored by the bios.
You may be able to set Intialize Video First or Primary Video or similar in the bios Setup to Onboard video, AGP, or PCI, but if the onboard is disabled by installing the AGP card, the Onboard Video setting (or Auto, regarding the onboard video) has no effect.
If the Radeon 7000 is a PCI card, the onboard video may or may not be automatically disabled when you install the card - it's most likely to be disabled if the PCI video card is in the last PCI slot closest to the center of the mboard - next to the AGP slot it has one.
You have not said whether the onboard video works when you plug a monitor into it's port when the Radeon 7000 card is installed, or whether the onboard video shows up in Device Manager in Vista under Display Adapters (e.g. Computer - System Properties - Device Manager) as well as the disabled Radeon 7000 - if the onboard video doesn't show up there, it's been automatically disabled by the mboard's bios, and any settings to do with the onboard video are ignored in the bios Setup by the bios. .
"Since I want to use both graphics cards ..."
A pet peeve of mine...
The term CARD is frequently mis-used.
Both the Radeon 7000 and the Onboard video are a video or graphics chipset on a graphics or video or display adapter, but Onboard video, which is usually built into the main mboard chipset, is NOT A CARD. A video or graphics CARD, or any other CARD, is removable and installs in a mboard slot.
The solution for Vista? Use a card with a newer chipset that Vista DOES support. That depends on what the capabilities of your mboard are as well. An AGP Radeon 7000 card is 1X/2X/4X AGP capable - if the mboard can't support AGP 4X or 4X/8X, there is probably no 1X/2X AGP capable AGP card Vista has the drivers for, or that Vista drivers are available for. You can get PCI cards with newer chipsets that Vista has the drivers for, or that Vista drivers are available for, for not much money.