If you actually own a legitimate copy of CS5 but have lost your key, there are a few "official" ways to recover it:
If you have the physical DVD box, the 24-digit serial number is usually located on a sticker on the back of the disc sleeve or the box itself. adobe master collection cs5 serial number
The search for an is a common journey for users looking to access legacy creative software. Released in 2010, Creative Suite 5 remains a sentimental favorite for many designers due to its stability and the fact that it was the last major version available before Adobe shifted toward the Creative Cloud (CC) subscription model. If you actually own a legitimate copy of
Adobe’s activation servers for CS5 have largely been retired or updated. Even a "valid" old key may fail to handshake with Adobe’s verification system. Adobe’s activation servers for CS5 have largely been
Are you trying to for a version you already own, or are you looking to install the software on a newer computer?
If you still have an old machine where CS5 is installed and working, you can use "Product Key Finder" software to reveal the encrypted serial number from the registry or system files. Moving Forward: Modern Alternatives