As computers age, they inevitably experience problems. They start to lag, parts may fail, the hard drive may function erratically and your software will not run as efficiently as before. There are many ways to increase your computer's functionality and speed, but occasionally you may be required to run diagnostics on your computer. The diagnostic tools can locate and correct errors, and you can run diagnostics on a Windows or Mac.
Open "My Computer" by double-clicking the desktop icon, or clicking "Start" and opening it from there. In Vista, this will simply be called "Computer."
Select the drive you want to scan, for example, your C: drive. Select "Properties" from the menu, and click on the "Tools" tab.
Under the "Error Checking" category, click the "Check Now" button. Check the two boxes in the pop-up window and click "Start." The computer will scan the C: drive to find and correct any errors on the disk.
Open a new Finder window and open the "Applications" folder. Inside this folder, navigate to "Utilities" and open that folder.
Open the "Disk Utility" application. Select the drive you wish to scan for errors, typically your Macintosh HD.
Make sure the "First Aid" tab is selected, then click "Repair Disk Permissions." This will scan your entire Macintosh HD for errors and correct them automatically. From this window, you can also verify and repair the disk itself for more problematic errors.
Before running any extensive diagnostics, it is helpful to back up your system or set a restore point, if possible, in case anything goes wrong.