need help in activating CS5 on a new (3rd) computer. Old laptop is inoperable.

Hi,

see >>> http://helpx.adobe.com/creative-cloud/help/install-apps.html here >>> How many computers can I install on
I quote: You may install software on up to two computers. These two computers can be Windows, Mac OS, or one each.

If you install on a third computer, it will request you to de-activate on the other two computers. You can then reactivate one of the previous two computers, and use Creative Cloud apps on it.

Hans-Günter