Hi guys,
I have a very very very frustrating problem here. I bought cod mw2 and couple of weeks ago. I'm not a huge fan, so i waited until two days ago to really play the multiplayer on steam. I clicked the mw2 logo, logged into a steam account, and then started playing as usual. from then on, if i wanted to play again, i WOULD just open steam, it would LOG me in by itself, and then i would click the logo in the bottom right to and then choose cod mw2 multiplayer and the GAME would start. today, however, while playing an online team deathmatch, someone hacked the game. my character froze up (i could see the others shooting at me though) and then someone used aimbot to own us all. i left the game and then joined a new one. but then i noticed that i had all the titles, emblems, etc unlocked. I then shut down the game. i logged out of steam (to MAKE a new account to play on) but then i found out that the game wasn't showing up in the new account i made. so now when i log into my old (hacked) account, the game doesn't show up either. can someone please explain what is going on here?
I try to reinstall the game using the CD, but when i enter the CD key, it says that it's a duplicate and is associated with another steam account. now wth do i do?
i can post pics of myself with the game if you guys want.

EDIT: This is on Windows 7. I dont think you guys NEED to know the rest of the specs, do you?So.. Your old account Steam account was 'hacked' and then you created a new Steam account?

You do realize that if you bind games to a Steam account, they're bound forever? It's no wonder the game says the key is already in use.
Also, you might want to contact Steam technical support.. I'm kind of surprised you haven't already.