When I try to start garageband it tells me that it can't find the library. I tried reinstalling it but it still can't find the library. If anybody has any ideas let me know. Thanks

If you mean the Loops library, it should be in

/Library/Audio/Apple Loops/Apple/Apple Loops for GarageBand/

HTH

Use the disk utility found in the utility folder to repair permissions, and or repair the file system.

I don't have the apple loops for garageband folder. How could it of been erased or moved. Garageband worked fine the last time I used it and when I went back I ran into this problem. How would I make a new folder?

I'd make a search for "loops" ti see if it's not somewhere else…

Then I'd look closely to the hard drive, first on the file system (using Onyx to execute the maintenance scripts, initialise the folder information -not sure about the name of the option in English). Then the hardware, it's strange a folder disappears like that!