My last Mac OS X tip(found Here) allows you to enable hidden folders in Mac OS X. Now if you have hidden folders enabled then you may be wondering what the .DS_Store file is in absolutely every single directory you go to?

The .DS_Store file is actually the way that spotlight is able to find things on your computer as quickly as it can. It indexes your directories whenever something changes, and that’s why when you plug in an external drive, it takes a while for spotlight to find items on it. This is because the .DS_Store file has to index the entire drive before spotlight can start finding anything. This means absolutely every single directory on the drive as well. So beware large drives can take a long time to index.

Hope this helps.

Cheers