I have CCleaner Professional Edition on my present computer. I bought a new computer since my present one was purchased in 2009. Do I need to buy another copy of CCleaner to install it on my new computer or is there a way to add CCleaner to my new computer without making a new purchase? Thank you.
Simply download and install the Free version. The simplest way to download the Free installer is from here: https://www.ccleaner.com/ccleaner/builds
Once installed open it and go to Options>About>Upgrade to Pro.
Enter you registered name and key as asked then click on register.
(The name/key will be shown in the one you already have installed in Options>About>License Information).
There's more on registering, and what to do if you have problems here: https://support.piriform.com/hc/en-us/articles/204043844-How-to-register-and-activate-CCleaner-Professional#if-you-get-an-error-saying-that-your-license-key-is-not-valid--0-9
If you only have a licence for one machine you should uninstall CCleaner Pro from the old one. (You can then put CCleaner Free on that machine).