(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )
Only if your registry entries are intact. If registry was cleared (via usage of some stupid cleaning program, or Windows reinstall) and you didn't record the key like it's described in pinned thread here, you'll lose it forever.
If registry is intact, you may get the key (how - again, described in pinned thread).