Can u update Bios with wrong OS

I've got a Dell Inspiration 531s whose service tag shows a Vista OS. But I upgraded to Windows 7 recently, and in chasing gremlins found to updates to my bios that were never done. However when I try to correct the OS on my service tag info, it only gives me an option of Vista or XP. There is a tab to manually choose the OS but it goes to a blank page. I doubt I can do the update when it's looking at the wrong OS, but I'm not sure. Any help would be terrific, thanks