There are plenty of things that can slow your computer down. If your PC is a beautiful gazelle, gracefully running along, then software issues are the hungry lion taking it down (and brutally eating it).
Backup/Restore/Transfer/Sync/Archive Data
Format Hard driveĀ
Factory Restores
Application And Software Cleanup
Install Patches/Updates/And Upgrades
Install/Setup Software Applications
Remove Viruses/Malware/Adware/Spyware
Remove DustĀ