monitor shows vertical green dotted lines

My Toshiba M35 Satellite laptop was purchased in 2003. Just recently it started showing faint vertical green dotted lines on the screen that tend to become worse the longer the computer is used. After about 30 minutes of use the lines become so bad that they distort words and pictures to the point where the computer must be shut down. If the machine has been used for an "extended" period of time (30 minutes), the screen will be completely black when attempting to restart windows. I am able to hear it restart (the signature Windows sound) but nothing appears on the screen. If the computer sits for an hour or longer it can then be restarted and the same process occurs. When I hook the laptop up to an external monitor the same problems occur. Other symptoms that have come along with these problems include:

1. Glitches on the Windows startup screen during boot-up.
2. After extended use internet browser becomes non-functional, i.e. when trying to scroll up and down only about 1/4 of the browser actually moves.

I have scanned the system in normal and safe mode using two different anti-virus programs and have found nothing. I would appreciate any advice!

My first reaction would be HEAT!

Do you notice it getting hotter with use?

Have you ever tried to clean it inside?

I have not tried cleaning it yet, but this is something I will try. It does get hot with use and it has been this way for quite some time.

I am not familiar with the model but could look it up if you are uncertain how to get inside.

Sounds like either your CPU or GPU or both are just overheating.

A can of air might help. Also check the fan.

Thanks again, I will pick up a can of air and give this a try. If there is a website with instructions regarding how to get inside that would be helpful.

Best

http://www.irisvista.com/tech/laptop.../satM35X_1.htm

Those M35, and I believe, M30 Toshibas have a history of motherboards going bad.
Recently, exactly same Toshiba, with exact same problem was brought to me, and I tried all kind of stuff to no avail.
Finally, it was shipped back to Toshiba, and the motherboard had to be replaced.

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I tried opening up the computer and "dusting" with a can of compressed air. Everything looked pretty clean. After putting the computer back together I still have the same problem. I have read a lot about the motherboard problems as well. It seems that the cost of replacing the motherboard is almost the same as buying a new computer. Any other suggestions?

Replacing the motherboard in 6 years old laptop is out of question.
These days, you can buy decent laptop for about 500 bucks.
I bought one recently for $450.

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Thanks for all the help. I appreciate the input. I just have two questions 1) Is there any way I can test the motherboard to be sure this is the problem? 2) Any advice on what kind of computer (laptop) to consider purchasing?