The only .exe files that I back up are my installation files. I put them all into a folder called C:\Installation Files. I then back up this entire folder to Google Drive, since you get 15GB with Google Drive.
You could also back them up to www.4shared.com. They give you 15GB as well, but it's not sync'ed with your computer. In other words, you can offload your installation files there if you want.
I also back up my files to a Flash drive.