Hi and welcome to the Gigabyte Forum.
You main problem is I suspect that you are running a 32 bit operating system and that will only be able to use roughly 3GB maximum memory. If you want to able able to use more you would need to upgrade to a 64 bit system.
The problem with the machine restarting all the time is that the memory isn't matched or you haven't got enough voltage on the memory controller.
Hi and thanks for fast respond
The memory's are DDR2
So in case that there is not enough voltage , that means that l have to buy another better power supply ?
For matching l have try all the possible things
And to be honest l don't have idea how to upgrade from 32 bits to 64 bit , can you advise me
Regards
luli