Parallels offers a free full (not trial) activation key for its Parallels Workstation 2.2.2222 after filling out this short form link also given below. It supports 32-bit versions of Windows and Linux and typically costs $50/£37. The code will be sent via email.
Just need a valid email address. Everything else is up to you.
If the HUKD screws up the link then get your key from this link: