If you want to get the best experience you should wipe the disk completely and reinstall the OS. Do this with DBAN on a flash drive (install it with Rufus) and booting it in the bios. Have anything important backed up of course.
And the OS choice is up to you, I guess it depends on the system it runs on. If it was running XP then it probably wasn't designed with the performance/is too old to run something like 10, maybe try 7 or even linux. Use a flash drive and install the OS boot disk iso with Rufus like before.