You'll lose all of them, since a format erases everything.
The main concern is what Windows itself will support, which falls into a few categories.
1 - Really basic stuff that Windows needs to run (video, etc.). Windows generally has built-in drivers for these that will always work, but don't work best (for example you can't do any gaming on the basic video driver), it's meant just so you can use the computer long enough to download and install the drivers.
2 - Older hardware Windows has driver records for. Windows will install this stuff for you automatically like with #1, but these you don't need to worry about updating since they're relatively basic.
3 - Drivers Microsoft/Windows knows about, and can download through Windows Update and such for you. This works semi-well for some hardware, but needs an internet connection to work.
4 - Stuff Windows has no clue about. For this you need to download the drivers from the manufacturer's site.
You should have the drivers for all your hardware. Generally this is your motherboard's driver package, and any drivers for addon cards (video card, additional sound card, etc.) and anything else plugged in (webcam, etc.)
http://www.piriform.com/speccy
Running that program can give you some hardware models (for like your motherboard and crap) so you know which sites to go to.