Currently Being ModeratedNov 10, 2012 7:57 PM (in response to squierjosh)
Before disassembling the iMac for hard drive replacement, you might want to purchase Alsoft's DiskWarrior. Even before the introduction of OS X, it was always recommended for its superior "directory correction" capabilities. It is possible that the original hard drive has an electronic and/or hardware problem that causes it to create data errors when writing to the disk. You may find that after running DiskWarrior to clear up another problem, random directory errors persist. If so, you can decide if you want to replace the drive.