There are MANY reasons for computer slow downs:
not enough memory
too many programs starting up with windows at boot up time
too many junk files
too many restore points
Clean windows registry can speed up the computer.
Over time, you install new programs, uninstalled unimportant programs, update software's, install new devices,
download files from the web, etcetera, hence embarking all records in the registry system.
This is normal, but it is not wise to leave it untouched.
Once in a while, you have to check and remove files that are no longer in use to maintain the speed of your PC.
Clean registry make pc faster.