As you can see I have two problems.

I have a Toshiba Tecra A3 computer. It is 5-6 years old and it is connected to a D-link router.

For a period now it has not been working correctly. The computer freezes either when i try turning it on or when I have been using the computer for a short period of time.

The times the computer works normally I have a problem with a disappearing wireless network icon, and so I have no internet.

Can this be fixed or do I have to buy a new computer? I only use the computer for internet surfing and easy tasks like word etc, so I would like to keep it as long as possible.