I know that I have read this somewhere before and I'm not sure where. But does anyone by any chance know of a way to double check which cd-keys im using for d2. I could have sworn there was a way to search using regedit but when I tried that I was unable to find it

Regedit is not the location any of the Battle.net game CDKeys are stored. For D2, it's in d2data.mpq, and patch_d2.mpq for LoD, I believe. If you want to 'double check', just load a bot using one and try connecting on the game. If you can't get on, it's that one.