Here is a solution that I found, and it has worked for me, so far.......
My guess is your laptops are exhibiting the same problem I faced, random crashes and freezes, with no warning.
I replaced the hard drive, reinstalled windows vista, same result.
Replaced ram, no better.
Replaced power supply, no good.
Run in safe mode, works fine, but very limited use.
Removed all the startup programs, still crashed.
Pulled my hair out, that worked for 10 minutes......
Replaced CPU, new thermal paste, reseated everything, and reassembled, and it worked perfectly, for about 3 hours, and then started crashing and freezing again.
Replaced vista with 7, and it wouldn't start at all........
Then I found a forum article that suggested that it only occurred when BOTH the battery and AC power supply where plugged in, disconnected the AC, started on battery only, and the problem seems to have completely dissappeared.
Not a solution, but certainly a step in the right direction. Now it appears then that something causes the computer to freeze on the motherboard at the AC point, or in the connection between the AC and the battery.
Forum suggested changing a bios setting.
Change the following setting in the bios setup, under the 'Advanced' tab
Dynamic CPU Frequency Mode = Always Low (NOT DYNAMIC)
Save and Restart
Now, this laptop has been running on battery only power without a problem for 2hours without a hitch, I was lucky if I could get 20 minutes out of it before, and most times it would not even start.
I am about to connect the AC power (whilst running) to see what happens, so I will report back on the result in the morning after it has been running for 5 or 6 hours.
Hope this helps. Will report back with further results