Reinstalled the system yesterday, and i would like to install all my games (GOG, Steam, Impulse,EADM ) on a different partition. Is it possible ?

You need to have Steam installed on said partition and games will automatically install there. Otherwise, well... Just install it on the new partition and you'll have no trouble with it, I myself have partition only for games.
edit: Oh, what applies for Steam applies for Impulse as well.

Choose E and not C. Simple.

You can install GoG games anywhere you want.
Steam games are installed where Steam itself is installed.
Impulse let you choose the folder where downloaded games (all downloaded games) are installed (unless they changed that with later impulse version havent tried recently), I don't know how it work with "retail" version using Impulse/GOO as DRM though
And I don't know about EADM.

Well, regarding Steam, you can actually have the software installed on one partition and the games on another but you would need to create a symlink to the new folder and, even though it's not that messy, it's not really recommended.

I've always installed my games and steam on a separate partition. If steam is on a different partition from the OS, all you have to do is reinstall the steam client back to same folder after the OS install/reinstall and all the games with work without re-downloading. They will just set themselves up again like a "first run." Also, some more recent physical media based game's installers can detect the presence of the game files and just setup the registry. An example with this capability is Battlefield 2 and 2142. EADM allows you to set folders for downloading and installing games in it's settings. I don't do Impulse but I'm pretty sure its like Direct2Drive in that the user can install anywhere.

thanks for the help guys