After a portable hard drive failure this summer (the dreaded whirl and click) relying on a piece of hardware wasn't going to cut it. Dropbox, Box, OneDrive are some of the cloud choices I use to store my docs and pictures but I decided to start syncing my most important Windows folder to Google Drive. First things first, download Google's Backup and Sync.
The next screen will show that Desktop, Documents and Pictures are the default folders that will sync to Google Drive. Here' the important part, click on Choose Folder and pick a folder to sync.
In Step 3, uncheck the Sync My Drive to this computer. This will prevent the folder to sync back down to your PC - remember you're using this as a backup. Investing in another portable hard drive was still something I had to do, but having that safety net in place was ace!