Vista - laptop locks up intermittently?

Toshiba laptop running Vista home premium locks up intermittently. There is
no pattern. When it locks up, everything stops responding and you have to
switch off/on the laptop. Checking event viewer, you get:

The previous system shutdown at time on date was unexpected.

I think when you switch off the laptop, above entry is generated. Could not
find any other relevant entry. I have done the following:

1.ruled out over heating.
2.Ruled out start up services
3.ruled out antivirus
4.ruled out power options
5.reformated hard drive
6.passed hardware diags

Still the frustrating problem persists.

Any suggestions on how to fix this problem?

Right-click Computer, and choose Properties. Go
to "Advanced system settings," click Settings under Startup and Recovery.
Under System Failure, uncheck the box "Automatically restart.
Now when the problem occurs again, instead of restarting, you will get the
blue screen with diagnostic information. Post back with those details for
more help.

"computer1" <computer1@xxxxxx> wrote in message
news:2D4002C6-5040-48CB-AA64-5E4E3EB02CFD@xxxxxx

Bob when the problem occurs, computer does not restart. it simply freezes.
any other suggestions?

"Bob" wrote:

Hi computer1,

Next time you start your laptop, enter the BIOS (refer to the user manual).
Check that everything is set to its defaults. If your BIOS has a 'System
Health' page, go to that and leave it on that for a while. Are the values on
that page stable? Also, enable memory testing in the BIOS. Does your system
have trouble booting with this option enabled? Random problems like this
point to RAM faults. Remove the RAM and reinsert it. This action cleans the
contacts and can even solve some of these types of problems. If not, try
replacing your RAM.
Dwarf

"computer1" wrote: