How to download Parallels Desktop Version 4.0?

I bought Parallels Desktop 3.0 last fall, and then received an e-mail with an activation key for a free upgrade to version 4.0.

I am now rebuilding my flakey Windows XP installation, and figure I might as well upgrade to Version 4.0 while I'm at it. But now I can't find any link to download Version 4 -- the only links I can find on the Parallels website now go to Version 5 (which I would have to pay for).

Is there any way to download and install Parallels Desktop Version 4.0 at this point, or is it gone forever?

Matthias