Empty ProApps Folder????

Hi there peeps!!!
First post in forum, but have searched and can't find similar issue so here goes....
I have a 15" Macbook Pro, 1st Gen, 2,4Ghz, 4MB Ram, which was loaded with all of my music/design software (Logic 9, CS5, Final Cut Pro, etc), all of which was working fine on Volume Licences....until today. I am new to Macs having used PC's forever but am NOW a convert.
Today I did a software update which updated virtually everything, but since doing so I am now asked for a serial number for Logic 9 ONLY!!! I don't currently have access to this info as partner who used to own machine is away, but having researched online I have found a way to sort it by amending something in the 'ProApps' folder. However, my 'ProApps' folder is completely EMPTY and doesn't even appear in the usual place (Library/Application Support/ProApps). It actually appears in Applications/Applications/Applications/Library/Application Support/ProApps!!! Is this the cause of my problem and if so, any idea how to put the folders back where they belong?
Or is there a way of 'backdating' my machine to a time prior to the updates, similar to system restore on a pc?
Many thanks for any help anyone can give me.

A.

You need the original install media and the license serial numbers that came with it. Do you have them? Did the person who sold the machine to you include them with the machine? Otherwise, the software is not legally registered to you.

They are at my business partners houe but like I said, he isn't around for a while. I heard that removing an id number woud reveal the original serial number, but like I said I can't find the ProApps folder with any info in it. :-(