You know the old saying: "If it ain't broke, don't fix it!" With computers, though, things can be broken without manifesting any obvious symptoms. You can nip many such problems in the bud with a simple procedure that looks for, and fixes, common disk errors that can crop up over time without your knowledge. I recommend doing this not only as an initial step, but also monthly.
To repair your disk, follow these steps:
Start up your Mac from media other than your regular startup disk that also contains Disk Utility. This could be, for example:
A bootable duplicate of your startup disk stored on an external FireWire hard drive (or a USB 2.0 hard drive, if you have an Intel-based Mac), a second internal drive, or a second partition of your main disk
A Mac OS X installation DVD or CD
A TechTool Protégé device, to which you've copied Disk Utility (www.micromat.com)
You can't repair the disk from which Mac OS X is running (or the disk from which Disk Utility is running, if it's not the same one); that would be somewhat like trying to perform brain surgery on yourself. You can, however, verify the disk (by clicking Verify Disk in Step 4) to determine whether there are problems that Disk Utility could repair.
Run Disk Utility. (If running from a cloned hard disk, you can find it in /Applications/Utilities. If running from a Mac OS X installation disc, click through the language selection screen and then choose Utilities > Disk Utility.)
In the list on the left side of the window, select your main startup volume (the one you want to test), as in Figure 3.
Figure 3. Select a volume (other than the startup volume) on the left, and then click Repair Disk.
On the First Aid tab, click Repair Disk.
Disk Utility looks for common errors and repairs them if possible. Ordinarily, it displays a message saying that repairs were completed or that no repairs were necessary. In the (rare) event that Disk Utility encounters a serious problem it cannot solve, you may need to use a commercial repair tool such as DiskWarrior (www.alsoft.com; $80).