win 2000 product key-not in belarc

Hi all ! just joined-NOT an IT guy, just like to build sys,learning(slowly)lol!! to tweak & recover my own crash-N-burns-call me weird, but I still like 2000 over XP !Had to u/g anyway,(sick of constantly re-formatting finally) and when I did, my office 2000 sr1 pro lost ?start menu?-and required product key to re-install-the switch to XP PRO did something, and my OEM key was now not valid-a friend found and installed a valid key, but didn’t write it down,and when I used Belarc, the only office key that showed up was for my beta build office 12(now expired)-any other suggestions for retrieving this key?-I don’t wanna have to go through this again if I swap M/B’s or H/D’s-still have a good copy of all programs on extra H.D.-prepared for the NEXT crash !! lol