Technically, although Skybolts response may have been curt she is correct. Unless you have the license keys on their license forms or in the book (depending on if they were on stickers and placed on the manual or even on the pc itself) or possibly the official print from the purchase (ie: if it were a web purchase where no hard copy material were received), the software is not legitimately licensed to you - which technically makes it pirated software, even if you didn't do it yourself.
Now, either the original owner still holds the license (which means, technically, he should have wiped the software off the system before selling it because by allowing you to use his license while he still holds it is illegal), he *really* did loose all of his materials and documentation on the software (I know I've never lost *every* thing for my software before - although I have lost key components like on a version of Premiere that came with one of my non-linear editing systems bought new by me and I've successfully lost the license form although I still have the hardware, manuals and the original CD) which means if he originally sent in the registration forms he may be able to get the info back from the companies with appropriate proof of who he is; and of course the last option - the software was never legally purchased and is not a legal copy.
Many sellers sell systems on ebay with software on it that shouldn't be there as "added bonuses" usually claiming the software being there for you to "try" - ebay doesn't check the listings closely, but if they do stumble across computer listings like that, or have them reported - they usually nuke the listing.
Now, does that mean you can't try to copy all of the relevant files and hope it works - no, it doesn't - but by doing so, you are perpetuating the illegal action, and at these forums, they are sticklers for copyright and legal software only (which is understandable as they follow the US copyright laws and have that mentioned in their forum rules) which means that they basically will refuse to help, and many times lock posts that request help with potentially illegal software, including getting, moving, copying, etc. (this also includes topics on ripping video, assuming you're doing it to try to copy a movie that isn't a home made one where you are trying to get around copy protection).
Also keep in mind, sometimes even transferring license keys doesn't make it legal to give someone else software as many (not gonna say all, as there are several that do permit it) license agreements bar transferring a license to a secondary entity.
This means, even if someone knows all of the files, folders and whatever else might be needed to be moved - they probably aren't going to reveal that info.
Oh - and don't ask me how to, as for one thing I don't know as I've just recently switched to mac, and although I have a lot of unix and linux experience, i don't know where everything is stored on the mac - and even if I did, I don't want to get booted off the forums here
ps - I was still typing mine when cwa posted - lol, guess I was being long winded.