Complete newbie, so please bear with me....I have an old Gateway 420GR PC with no video card, just integrated graphics on the mobo. If I upgrade the video with a plug-in card, do I need to delete old video drivers? Also, looks like the newer video cards are PCI-e 2.0; should they be compatible with a mobo having only PCI-e slots?
You would need to turn the onboard graphics off. Install the new card and load drivers. The newer PCI-e 2.0 cards are backward compatible with your PCI-e x16. But I dont know your board and assuming you know the difference between a PCI-e x16 and a PCI slot.
PCI-e 2.0 cards are not necessarily compatible with the older PCI-e 1.0 slots. Some cards in the 8800 line and possibly the 48xx line don't have a "profile" or something like that for PCI-e 1.0 and won't work in older motherboards. Found this out the hard way with an older 915 motherboard with an 8800GT 256MB. ended up needing to upgrade my motherboard.