I bought the perpetual license for Lightroom 5 in December 2013 and it's been working fine. I installed it on an external drive and recently my computer has had a hard disk failure. I copied over all files onto this same external drive before it really failed. When I went to go use Lightroom again, I accidently clicked on the Setup.exe as the directory structure was different than I was used to although I stopped it before it did anything. Since then, it's telling me I have to do a trial or buy Lightroom again. It's not starting or giving me the option to enter my serial number and get going again eventhough I've paid. I'm not sure if accidentally clicking on the .exe was the issue or if there were files on my hard drive that were actually being accessed by the external drive unbeknownst to me. Is there anyway to get Lightroom working for me again?
It sounds as if you have installed the trial version of Lightroom 5. If that is the case, when the trial screen appears telling you how many days you have remaining, you will see an option on that page to indicate that you have a serial number. If you choose that option you will be guided to providing your serial number and that should take care of everything.