Reinstallation

"I am going to have to rebuild my computer. I have my CC Cleaner Pro + license key but I don't have a CC Cleaner disk. When I am ready to reinstall on the rebuild will I be able to download a copy of CC Cleaner Pro + and then use the license key I have now."

It isn't a problem, all CCleaner installs are downloads. (There's no disks unless someone makes one themselves).

See here for the easy steps of how to do it: