'code 12', and can't put laptop to sleep?

i've bought a new hard drive for my computer as the last one kept looping on startup (but that's just a peripheral detail), installed windows vista, then got myself all the newest drivers for my laptop from the acer website (as it was acer that made it.. again, just peripheral details, for context) .. all the driver software loaded up fine and are working fine, except the one for my video card, which has a little yellow warning triangle next to it in device manager .. when i look in the properties dialogue box for it, it says

This device cannot find enough free resources that it can use. (Code 12)

If you want to use this device, you will need to disable one of the other devices on this system.

Click 'Check for solutions' to send data about this device to Microsoft and to see if there is a solution available.

and underneath that is a 'check for solutions' button, which does nothing except tell me that it can't check for solutions.. .. i've had a look on other sites, and the only advice i've managed to find is to click a button that says 'troubleshoot', which people have usually said should be where that 'check for solutions' button is (so please don't tell me to click troubleshoot, as there's no button for it.. unless i'm looking in the wrong place.. where else would it be?) .. .. yea so how do i find out which device is conflicting with the video card, and how do i fix this? thanks very much in advance