Somehow, I never had the problem with it. I installed the full MoW first and then I installed the VDE (I had a problem with the Russian patches so I tried VDE as a solution) and when the free trial period ended it just asked me for the key and that's it. I am still using the same Gamespy account.
With a different game, I noticed that Gamespy is letter case sensitive. It is best to stick to the original letter case when typing the key.
P.s. Use you low rank and high experience to suprise your opponents.