The Encryption Desktop PGPtray.exe is not a Windows service, but is part of the Windows StartUp applications. A shortcut to it is found in "C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp"
If the PGPtray isn't launching, it is possible the existing shortcut is corrupt. Create a new one from "C:\Program Files (x86)\PGP Corporation\PGP Desktop" on 64-bit systems, or "C:\Program Files\PGP Corporation\PGP Desktop" on 32-bit systems, by right-clicking the PGPtray.exe file and choosing to Create Shortcut, then move that shortcut into the StartUp folder. Windows requires Administrator rights to do this. The old shortcut can be removed.