Ok i bought my game,please tell me how do i download the game.i have the space,my hard drive is 320 gigs.Thankyou very much.

Hi.
You just have to go to 'My account' page and click on the game cover. All available files (setup and extras) will be there available for download.

Be aware that for Spellforce you'll need to download three files (two bin files and a small executable) as opposed to the single file typical for most other GOG games. Just make sure that they're all downloaded and in the same directory, then run the executable to install Spellforce.