I want to download my gog games to my external hdd for backup. When I try to do this the game tries to install on my C drive. I don't want to install at this time. How do I do this? I have Win 7.

You probably use GoG Galaxy, so click on More -> Download Backup and Extras and download the installers there or use the website to download the installers.

Not sure how to do that, but what I do is just download my games to C drive, then copy and paste the installers to other storage.

Edit: This is using the standard download through browser method, not using Galaxy.

When you go to your library and click on the download link *not in Galaxy* the launcher will open, in the upper right corner is a settings button, click on it and you have a choice in a drop down menu as to where you want to save your games.

In your library click on the picture (not the little button that appears when you hover over the picture) of the game in question.
You get a pop-up. In that pop-up either click on the game download itself to download via browser or click on "More" and choose the GOG Downloader link if you want to use the Downloader.

From your web browser (NOT GOG GALAXY):
1) Click on Account in the top menu.
2) Click on a game you wish to backup.
3) A Window will open.
4) Click on any file you wish to backup.
5) Save it to wherever you wish.
6) Return to (4) to backup more files from the same game, until done with this game.
7) Once done with this game, return to (2) to backup the next game.
8) Enjoy.