KB Parallels: How can I find my activation key for Parallels Desktop?

Plesk 7.5.x Reloaded; Plesk 7.1.x Reloaded; Plesk 7.0.x; Plesk 6.x; Plesk 5.x. Parallels Plesk .... I lost the activation key for my copy of Parallels Desktop for Mac.

kb.parallels.com