Although Disk Utility reports that the Disk "appears to be OK" it does not do a real in depth check on the drive.
If this is the actual cause, then the replacing the drive would solve the problem.
You could try creating a new admin account, logging into it and seeing if the problem is still evident, before you consider replacing the drive
Well, my Macbook 13" running OS 10.5 is stiff and sluggish. Just out of curiosity, I downloaded Sophos Antivirus Home Edition and ran a scan of the whole hard drive. The scan turned up nine problems, all pertaining to Windows only (who knows how I got them). I tried following the instructions for manual cleanup, because there is apparently no other way to get rid of the files. I was unable to drag the files to the Custom Scan window, so that was that.
My question is: What else might be dragging my computer's performance down? The trackpad doesn't respond well; the keyboard is still (and I've adjusted all those settings); sometimes, I can't drag windows around; and that is just the tip of the iceberg. I've no clue why this is happening.
I've run Disk Utility, and permissions have been repaired. The hard disk "appears to be ok." I've replaced the directory with a new one in Disk Warrior. I don't keep a lot of windows open. I've unplugged the Mac for a while, then plugged it in again. I've shut the computer down in this very hot weather. (The sluggishness actually predates the change in the heat.
Well, the nice part of this afternoon is that I happened on a program all about old-style blues music. The blues make me happy. Go figure!