When you install the upgrade, you will be informed of what can and cannot be saved. You can make your adjustments accordingly. For instance, some apps might not be compatible with windows 10 (smh) but they will give a text layout so you can reinstall/re download/etc what you want. Also as a precautionary measure backup all of your files, settings, etc that you want to keep. You might also want to make some form of recovery media just in case. Prepare for the good and bad right?