Windows 10 Reset

I have a W10 computer that isn't working vary well and want to do a full reset to see if that helps. This computer started out as a W8 (or 8.1 am not sure) computer and the recovery image that I have is the original.

I do have dvds with the free W10 upgrade that I took when the operating system was upgraded.

Can someone tell me the best way to get back to a fresh W10 installation under these circumstances? Will it reset to W* and then I reinstall from the DVD? If so, what do I use as a product key?

 

Before you do something so drastic have you done a good cleanup of the computer? Run Disk Cleanup and/or CCleaner and then scans with all of your security programs, av, Malwarebytes' SUPERAntispyware, AdwCleaner, Junkware Removal Tool to be sure there is no junk that is slowing things down?

 

Done all that. Just want to know the procedure before I start.