When I built this computer back in the dark ages of 2007, I set it up to dual-boot Vista and XP. Every time I powered on, I'd get a prompt to boot into Vista or "older version of Windows," meaning XP. I'd pick one and go on my merry way. In 2011, I formatted the Vista drive, installed Windows 7, and deleted the XP install since I had XP mode in 7 if I needed compatibility. No more dual-boot prompt. I had no issues until last night, when I went shopping for a new hard drive. My motherboard, a Gigabyte GA-P35-DS3L, was running an old BIOS that has problems with drives of 1 TB or more. So in order to be sure I could use the drive I'm buying, I updated the BIOS to the latest revisiion, using Gigabyte's @BIOS utility to do it in-OS rather than through the boot menu.
When I rebooted, the system POSTed fine. But instead of booting Windows, it gave me the old choice between Vista or the "older version of Windows" - despite neither of those operating systems being present. If I tell the boot manager to do anything, it spits out an error since it can't find any OS files it recognizes. The BIOS itself seems to be fine - I'm writing this on the affected computer, running Ubuntu with a Live CD. I can see all the hard drives, open files, etc. I just don't know how to get the boot manager pointed at Windows 7 again. Help?