your cd key already in use red alert 3

[cat]

i can't play with my friend i keep say key already in use how to fix this :(?

[Taboo]

Im having the exact same issue with a friend of mine
we are using Hamachi to connect

but its odd, if I create the match, I can play with no issue, but he cant join (gives CD key error)
but he he makes the match he can do it with no problem and this time I am the one getting the CD key error

[Xan]

The CD Key is by default stored in the registry at HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Electronic Arts\Electronic Arts\Red Alert 3\ergc

Steam writes your CD Key each time it launches RA3.
The problem is that it's no longer supported so everyone ends up with the same CD Key: %CDKEY% hence the error that it is already in used.

You need to change the CD key and launch the game without Steam (double click RA3.exe for example) and you will be able to play with your mate.

[Cat]

Hmmm. Time to reunite with my old friend: Windows Registry.