How are you adding you music?
Open Preferences>Music Library>Add New Folder
Using the add file/folder from the main menu can be problematic for large numbers of files
The speed of your computer can affect the time it takes to do the initial scan
My 150g of music will take around 1/2 hour on machine with 8g of ram
I don't know what operating system you are on, but deleting the configuration file can help, uninstalling can leave it behind