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I don't mean to be rude, but you guys have zero idea what's causing this issue in regards to STEAM purchasing Crysis Wars. The issue is VERY simple and VERY easy to fix.
The Cause is 100% steam's fault. When STEAM installs Crysis Wars it does NOT format the CD-key correctly whatsoever. You can view this by uninstalling your Crysis:Wars from your computer. Go into your registry & clearing the cd-key out, and then reinstalling from steam's STOCK install process for Crysis:Wars. Viewing your "STEAM installed" version shows that there are absolutely ZERO dash marks ("-").
I just recently picked up Crysis:Wars via steam JUST to try & play MechWarrior:LivingLegends because i've been bored & wanted a good Mech game to play. Right out of the gate I got that "Dreaded" cdkey error. What did I do? Googled for 10minutes, found the solution, put the dash marks in my CD-key's registry location, and BAM no more error.
Since then, four other of my friends got Crysis:Wars from STEAM to play Mechwarrior:LL, and another 5th already had Crysis:Wars (boxed version) & proceeded to reinstall it. Guess what? ALL four of my friends who purchased from steam got the CDkey error, but my 5th friend with the box did NOT. Simply putting the dashes in resolved the matter completely (go figure).
By all means, keep calling EA or STEAM support about this issue to get more keys (stealing?). I've already spoken with a rep from EA about this & they've confirmed the issue (they'll no longer give out keys if you bought it from steam, or at least what I was told "lol support").