What is the difference between a DDR2 and a DDR3 memory card and can it be used interchangeably from one platform to another?

There's no sound coming out from my laptop. Tried checking the volume and even used external speakers but it doesn't work. I have Windows Vista installed. Any help will be greatly appreciated.

My PC was working fine before the problem occurred.

When I press the power button the power led lights up but then nothing happens.

The HDD led blinks once or twice then nothing at all but the power led remains on.

Any idea how to solve this?

I have a Sony Vaio E series laptop. The laptop came out with Windows 7 installed and only one partition. Recently I used partition magic to make two more partitions and most probably made a mess of it. In the next boot my laptop says MBR not found. Any idea how to fix this?

Whenever I try to play a game or do anything with any of the adobe software, after running for 10 minutes or so, the program crashes and says something like "memory location could not be read".

I have tried re-installing windows but the problem remains. So I guess it's a hardware problem. I desperately need help on this please!

I just recently formatted my desktop. Right after installing the drivers for it and rebooting the computer the final time I got this message on my computer "Out of range". What can I do about this? Please help me. Thank you.