MangorushZ: I tried to redeem the key from the enhanced version of Baldur's Gate 2 to add the original version to my library like I did for the first game but it doesn't seem to work, do they no longer let you do that anymore? If not, that is a totally a shame.
"Same" issue for me... but it's for BG1 instead of BG2.
Maybe i can help you a little. With Gog's website, i could'nt redeem my keys for that 2 (fantastics!!!) games.
I tried with the soft GOG Galaxy. In the soft, click on the GOG log top the top-left, then "redeem key", and past the key (only the key, not the full link) found in your gog's library on the website.
After a second try, my BG2's key has been redeemed and i've got "Baldur's Gate II Complete" in my library.
But it doesn't work for my BG1 :(
Try it, hope it works for you.
(Now, i want BG1 classic too ! ;____; )