I backup all my wanted data onto an external hard drive, if you only ever do one thing to maintain your computer system so that it works at it's best, the one thing you should do is a complete backup of all your wanted files/folders, then do a complete reformat of your computer's main hard drive, or the one marked C:, then do a complete clean install of your computer's operating system, do this every 6 months.
When I do the Backuping/Re-Formatting/Clean OS Install, I usually do it in this order:
1, Backup all wanted data.
2, Re-Format the C: Hard Drive.
3, Clean Install the Operating System.
4, Install all Device Driver Software.
5, Download all OS updates after getting the computer back online and registering the OS.
Usually by then my computer is fully up and running and then I'll install all my music making software.