What’s the safest and fastest way to back up my PC before a clean install?

If you use Drive for Desktop, be careful with the difference between syncing and backing up. After reinstalling Windows, downloading the files through the Google Drive website first is safer than immediately reconnecting an empty or partially configured sync folder, since an accidental sync setup could propagate deletions or changes. Also, a clean install is not always necessary unless you have a specific reason for doing one; make sure your current problems actually require it.

Be aware that uploading a large collection can take many hours or even days, depending on your upload speed and any data limits from your internet provider. A few gigabytes is usually manageable, but hundreds of gigabytes or a terabyte would be much more practical on a USB 3 external drive. Cloud storage also shouldn’t be your only copy of important files.

The simplest approach is to install Google Drive for Desktop, choose the folders you want to back up, and let it upload them. You can also use a cloud-storage manager such as Air Explorer to browse Google Drive like another disk and drag files over. Before reinstalling, confirm that the files are visible in the web interface and open a few of them to verify the upload worked.

Try to make a complete backup rather than copying only the folders that seem important. Application settings and configuration files can be stored in less obvious locations, and missing one may cause problems later. At minimum, back up your personal folders, browser data, password or recovery information, license keys, and any application-specific data you can’t easily recreate.