Below are a few suggestions you can try to make your Mac run faster:
1. Is the desktop cluttered with a lot of images/music/files?
If so, clear–make sure you empty the trash.
2. Is the hard drive full or almost full?
Backup and save unused files onto external media: external HD/DVDs to free up space on your computer hard drive.
NOTE: THIS IS REMOTE STORAGE NOT A BACKUP. IF YOU HAVE MORE DATA THAN YOUR COMPUTER HARD DRIVE CAN HOLD, WE RECOMMEND TWO EXTERNAL DRIVES–ONE FOR REMOTE STORAGE, THE OTHER FOR BACKUP. Note that you should partition an external drive first before setting up time machine, which allows for remote storage on the other partition. You then need a backup of that remote storage partition.
3. Try running the mac in ‘safe mode’ – hold down Shift key on boot.
Is it still slow or is faster? If faster, there are probably superfluous programs running when in normal mode– consider changing your settings so those programs do not start on bootup.
4. Can try diagnostics to see if there is anything to check. – Hold ‘D’ on boot.
5. Is it possible to reimage/format?
This is the only sure way to fix the problem as it returns your computer settings to the day you bought it. First, try creating a new account. If the computer runs faster when you log into that account, you may have corrupt files in your profile, and not need to completely reload the OS.
If it is still running slowly after a re-image or re-format, then the computer may have a hardware problem. A computer can pass the diagnostic tests, and still have failing components.