I was able to use my 2007 install until I tried extending. I was only able to access the questions. I do not think the 08 cds will play on the 07 install. Can you extend your 08 materials with the short term extenstion.  I also had 2008 materials that just expired in feb.. so I dont have the materials ive grown accustomed to. I hope you get it.

Uninstall the program. Install the program again. They gave you 15 days to practice. You can change the date every day and 15 will never expired. For example : you practice on march 5. Then on march 6 before open the program, you can change the date of the computer to march 5 again. It is easy but difficult to explain for me because this is not my primary language. If you have doubt tell me.