I've got a XP 32 bit machine, Vista x64 never worked, with a P35 motherboard, including 2 PCI-EX slots, the first one with 16 lanes and the second one with 4. I've been testing an hybrid multi-gpu configuration, using an GeForce 8600 GT on the 16 lane slot for graphics and PhysX acceleration and a Radeon HD 4850 on the 4 lane for Stream computing, but either alone of accompanied the Radeon won't work with the SDK. The samples on the SDK won't recognise the HD 4850 even though the driver will, when it is on the x16 lane, but when it is on the x4 lane it won't be detected by the driver.
Can you tell me a workaround for this issue, or share other's experiencies about this?
As far as I know, windows (both XP & Vista) cannot load 2 display drivers at the same time. So, I would say it is impossible to do so.