I really like Sonic Foundry software; but their registration process is a pain. I understand why they do it, but it's a pain nonetheless.
When Sound Forge is first installed, it creates a special computer ID number based on your computer. You supply that number to Sony, and they e-mail you a valid key number based on your computer ID number. Once you enter the key number, the software is ready to use.
The only way you'll be able to use that software on your computer is if you enter your friend's original registration info. that he supplied to the Sony website. That's the only way they'll send you a new valid key number via e-mail.
I use ACID, Sound Forge, and CD Architect, and I've had to re-install them a number of times over the past few years. So long as you enter the original registration information correctly, they should send you a new number.