Toshiba laptop freezes after Vista reinstall

I have a Toshiba Satellite A215 laptop, which I've had for about 3-4 years.
I was having a problem with Windows Explorer hanging so I recently reinstalled the Vista operating system using the CD that came with the laptop. I did a complete format/clean install. In the 2 weeks since I did the reinstall, my laptop has frozen during use about 7 times.
What happens is, while I'm using the laptop the screen suddenly goes dark and the laptop will not respond to anything I do. The only thing that works is to hold the power button down till I force it to power off. I am then able to restart immediately without further problems, until it freezes again in a day or two.

Additional info:
Processor: AMD Turion(tm) 64 X2 Mobile Technology TL-60 2.00 GHz
RAM: 2942 MB
32-bit Operating System

A few other things that might be relevant:

-It doesn't seem to freeze in relation to my running anything in particular. Usually I am just browsing the internet, using firefox.
-The laptop has been running very hot for at least 2 years, though I now using a cooling pad with fan that does a great job keeping it cool. It has frozen both with and without the cooling pad under it.
-The laptop froze in the same way once right after I got it and once in the following three years. But the current problem began within a day of reinstalling Vista.
-I checked the device manager and nothing was displaying a problem alert.
-I have a 186GB hard disk drive with 84GB free.

Any advice would be appreciated. I have been considering upgrading to Windows 7 anyway, any chance that might help? I know it'd be better than Vista in general, but I don't want to buy the upgrade if my laptop is on it's way out anyway.

 

Nothing certain, I'm afraid, but you may have put your finger on it yourself when you said this:

Sounds a lot like you're running out of current. Does it happen whether running on battery or mains power?

Try this trick, just in case:
remove power cord and battery, hold 'on' button down for 30 seconds, then reconnect battery and power cord.

 

I haven't noticed whether I'm running on the battery or main power when it freezes, Though I'm pretty sure I have been plugged in to the main power at least some of the times it has frozen. I'll pay attention to that when it happens again. I'm not sure if by "running out of current" you mean the battery is running out of juice. If so, that is not the case. I do let the battery run down completely rather often and in those cases the computer shuts itself down and will not restart until I plug it in.
When I have the freezing problem, the screen shuts off but the computer does not power off until I force it to, however it will restart without my having to plug in.

If that's not what you mean, perhaps I should mention that lately I have been using a power cord for a different Toshiba Satellite laptop and it doesn't seem to charge my battery as well as my original cord did. I had been using this other cord for several months before I started having the freezing problem.

 

That's sort of what I meant, but there can be other ways of running out of power, in addition to a drained battery... poor connections, failing components, etc. These are more likely than a flat battery.
Interesting that you've been using a different power cord. You needed to check that the transformer output was the same (the box on the end of the cord). If it wasn't, it is possible that something has been damaged. However, since it runs for a day or two after freezing and rebooting, this is less likely to be the problem, I would think.
This also makes it less likely to be a temperature problem.
I guess it's more likely to be a software problem since a reboot fixes it.

You should check antivirus and antimalware apps, as suggested by Halo.
Also, have you installed all relevant updates since Vista reinstall?

 

D'oh! I think the problem may be solved. And I feel silly having overlooked so obvious a conflict, but since I appreciate everyone's advice, I'll post the details in hopes they may help someone else.
Basically, the problem was that I was running two anti-virus programs.
I installed Avast as usual after reinstalling the OS. But I forgot to change the Windows Security settings from their default "on" settings. So Windows Defender was scheduled to do a scan once a day. Which seems to pretty well explain why my computer would freeze once a day. :-o

 

Thanks for that. Another one to put under the hat!