you can repair a hard drive using disk utility->repair disk. to repair a startup drive you have to boot from a snow leopard install dvd or another hard drive.
there is no real need to defrag in OS X. OS X does a pretty good job of it itself. any files less than 20MB in size are defragged automatically. so long as you keep plenty of free space on your drive (at least 10%, better 15%) there should be no need to defrag and little benefit in doing so. Most OS X users never defrag.
there are no built in defrag tools. one way to defrag your drive (if you have to) is to clone it to another drive, boot from the clone, wipe the main drive and clone the clone back.
lastly there are some 3rd party defrag tools like idefrag. you can use them if you regularly work with many large files (>20MB) that don't get defragged by the OS. but use them with caution and definitely back up. a defragging can go bad and damage the drive.
you can repair a hard drive using disk utility->repair disk. to repair a startup drive you have to boot from a snow leopard install dvd or another hard drive.
there is no real need to defrag in OS X. OS X does a pretty good job of it itself. any files less than 20MB in size are defragged automatically. so long as you keep plenty of free space on your drive (at least 10%, better 15%) there should be no need to defrag and little benefit in doing so. Most OS X users never defrag.
there are no built in defrag tools. one way to defrag your drive (if you have to) is to clone it to another drive, boot from the clone, wipe the main drive and clone the clone back.
lastly there are some 3rd party defrag tools like idefrag. you can use them if you regularly work with many large files (>20MB) that don't get defragged by the OS. but use them with caution and definitely back up. a defragging can go bad and damage the drive.