It's a shame you didn't post the make and model. Some require a wired keyboard to get into setup (bios) and then set the date/time then enable USB Legacy or USB keyboard support.
This repeats on some older PCs as the owner forgets this or a shop set it up for them and didn't share the steps.
I've just become aware that my startup procedure is screwed up and has been for several weeks. When I Start up, the PC goes directly to the setup screen, where I have two options. First is "press F1 to continue; second is Press DEL to go to setup. I've been using W7 for perhaps 2 years with no problem; don't know why I didn't notice the first or 2nd or 3rd time etc. that I got the setup screen, but I didn't. Recently I had to replace the batteries in my Belkin wireless keyboard and that;'s when I saw the problem I tried a reboot with the new batteries but when the screen said "Press F1 to continue " my F1 was inactive!
I can get into the PC with a hardwired keyboard so the inability to sync the wireless board to the PC is not a major problem.
What concerns me is can I get back to the normal Start up sequence without having to re-install W7?
Will appreciate any suggestions

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic