Let's say you need drivers for the motherboard's components, but all you know is it's a dell, not the model number or anything. Open up that computer, and the model number should be printed on the board.
For instance, I have a ASUS P55 SLI, which is the number that's printed on the board, so I go to ASUS website, download the specific drivers, then things like USB ports, BIOs, Firewire, Ethernet are all working! This goes the same for any hardware component in your computer, although it might take some poking around to find those numbers.
Most of the time, you won't need to install ALL of the drivers to get it working for a arcade cab, but it's always nice to have everything working 100%!
An alternative is you buy one of those driver programs (Driver Max or something). There's companies that have programs that scan your computer and automatically download and install missing divers, great programs, but none of them are free. I'm cheap, so I never use them.
One last alternative is if you have the most recent version of Windows XP Black Edition, (Torrent... ILLEGAL!!!) when you install XP, most of the drivers will automatically be installed as well!
So there you go, information!!!