An Offline database can only be accessed from the computer that it was created on.
You cannot move an Offline database from one computer to another.
If you have somehow lost your Online (Master) database, and all you have is the Offline database, make sure you read this article.

If you're upgrading from Daylite 1.x to Daylite 3.x, make sure that you have read the following article which illustrates the recomended upgrade procedures: 
http://www.marketcircle.com/kb/idx/0/191/article/

If you are still able to connect to the Online database, and the data in the existing Offline database is not important to you, then do the following:

• Quit Daylite
• Delete the existing Offline database. (Instructions to do this can be found in this article)
• Launch Daylite
• Log on to the Online database
• Create a new Offline database (From the Daylite menu bar select File -> Database -> Go Offline)
• This will create a brand new Offline database for that computer.