Nemanja was referring to the fact you never said the 2008 version was the Premium version before. He thought you might be "upgrading" from Simply 9 Pro to Simply Basic 2008 because that is what you said, however, you cannot downgrade from Pro to Basic 2008, you can only go up to Premium or Enterprise.
When you copied the files to the client's computer did you just take the sdb file or did you take the sdw file also? If you ran a backup in Simply from version 9 and restored it to the client's computer, then it did take both files.
Can you open the sample data on the client's computer?
Version C is the latest program update for Simply 2008. Go to Help, About Simply Accounting when you open the sample file and see what version is listed there. If it is A or B release, then you should update to the latest version either through the SimplyCare update or from the program updates on the main website I inidcated before.