My question is not how to fix anything, because I have already replaced the drive in question, but how to diagnose some strange behavior, so I can give an objective reason for an RMA. I have been having significant problems with a number of apps in terms of their slowness, and a recent string of BSODs, which all seemed to point in different directions. After checking the software and system every way I could think of, I began looking at the possibility of it being a hardware issue. I ran a test with HDTune, just the day before the last BSOD, and the system drive looked okay, but when I awoke the next day it had crashed again, and hung on reboot at the Windows logo screen. After a couple of attempts to boot normally which failed in like manner, I ran the Windows Startup Repair Utility, but when it failed, it said that the reason was a bad hard drive. That is when I pulled a spare drive out of the closet to replace it with. As soon as reaching desktop, I ran HD Tune again, and when the benchmark screen indicated a severely low transfer rate, I ran an error scan with both HD Tune and Digital Life Guard. Both of those results were A-Okay, with no bad sectors. I then ran the benchmark on it again, and that time the transfer rate was normal. At this point, I have no idea of what the problem was, unless it was something to do with the logic board, but as far as I can tell, neither of the diagnostics that I use actually test that directly, other than reading the smart data. Now I have a drive that I don't trust, but can't point to exactly what the problem is. Can anyone suggest a definitive method of testing this drive?