Logic Pro 9 Install issue with 9.0


I am installing Logic studio upgrade moving up from Logic 7. Install was going as planned until it asked for the 'Additional content' disk - looked in the box and it hadn't been supplied! The screen told me I wouldn't be able to complete the installtion and the program wouldn't run properly. I tried running it just in case...but it didn't work - crashed immediately, and no other parts of the program will run such as Waveburner, either.

The shop have now sent me the missing disk. I put it in to see what would happen and instead of completing the install it's telling me to reinstall Logic again. As most of the program has installed, is this necessary? And if I have to reinstall, do I need to wipe the partially installed L9 or can I do it 'over the top' of the previous install and a new install will replace the old one?
Many thanks for any help.