After looking at the many threads in this forum and others where people desperately look for help but can't find a solution, here's an example of something that did work.
A two-year-old Gateway notebook running Windows 7 started crashing without warning. The computer would lock solid, then drop into CHKDSK on a restart.
Resetting Flash and Java did not work. Renewing video and sound drivers did not help. There were no troubleshooting logs left behind and no error messages left by Windows. There was one blue screen stop message that hinted of a memory problem, but a memory test showed no trouble.
Then, a couple of hard drive tests failed to complete, pointing to the drive as the problem.
The solution started by checking type of hard drive used by the notebook -- a SATA drive -- and finding a replacement. Fortunately, Best Buy had those drives on sale, so a 320 GB drive was purchased to replace the failing 160 GB drive. Then, the old drive was cloned to the new drive, using a SATA-to-USB enclosure. Both drives were Western Digital units, and WD makes a version of Acronis utility software available for free. That was downloaded and installed.
The cloning process took around three hours. When it was finished, the old drive was removed from the notebook and the new drive installed. It worked perfectly.
All of this is mentioned to show that sometimes, solutions to seemingly unsolvable problems can be found.