Stop screen – 2000 Pro OS can’t be found – pls help

My business computer using Windows 2000 Pro was hit by a power surge (despite my surge protector) and now shows the blue screen with “Stop: 0x0000007B” etc. after the title screen. We tried to upgrade to XP Pro w/a new CD, but it wanted to do a new install because it couldn’t find the old OS and I don’t want to lose everything. (I do have my files backed up.) Then I tried to re-boot 2000 from that CD to try to repair whatever was wrong, and it could not find the original OS either. My IT consultant (I’m not an IT person) finally said to call Microsoft which I am loathe to do, but will if I have to. I do not have an Emergency Recovery Disk since this computer came from my former company. Can anyone help me? I would be so grateful.