HI, I've already downloaded my library and was wondering if i can just install from there rather than re-downloading all my games again?

Galaxy should have an "Import Folder" function, so install from the installers and direct Galaxy to the folder you have installed your games. Galaxy should pick them up.

For more information about importing games to GOG Galaxy read this:

== IMPORT ALREADY INSTALLED GAMES TO GALAXY ==

1. For GOG games installed using installers from the last few months (so called Galaxy-compatible installers)
Click the "+" button on top of the sidebar and select "scan and import folders" - it will find all compatible games within that folder and add them to the Client.

2. For remaining GOG game INSTALLATIONS
Find the game in the Library (click on the image of the game), then click the More button and select "Manage" -> "Import folder" and point the folder selector into the folder where that game is installed.
Please be aware that Client will accept any folder pointed to and will overwrite files inside it (this can for example wipe some mods or damage other apps in case of pointing to a wrong folder) and will update the game to the newest version (current default language English).

Source: http://www.gog.com/forum/general/gog_galaxy_beta_2/post1

worked perfect thank you.

Edit: i spoke too soon. the frist two worked ok then when i installed more I kept getting this error which said no game files found. below are my steps.

1. install game from exe to games folder under gog cliet
2. find game in my library and select configure
3. on the main game screen, i pull down the more menu and select manage then import folder
4. i select the game i just installed (under the gog client directory)
5. error message

edit: fixed it.