no
Buy a new motherboard and replace the old by the PC engineer that fixed the same PC unit.
In order to upgrade SDRAM with DDR, you will need to replace your motherboard. DDR uses a different slot than SDRAM, so if your motherboard is using SDRAM currently, you will most likely have to replace your motherboard in order to make your system support DDR.
No. You would need to replace the entire motherboard.
Yes, it is possible to replace your motherboard with new one. Just make sure that your new motherboard fits in your computer, and that it support all of the hardware you had on your old motherboard.
$200
NO both were indipendent
assuming the older mother board has similar sockets and slots for your current devices parts (and your motherboard supports those devices) you should have no problem downgrading
No. The PCI slots on the motherboard will not line up properly with the chassis and most chassis that are made for ATX have screw holes to accomodate atx and mini atx
yes, but you'd have to replace the motherboard as well since it's integrated into it.
No. You will need to replace your motherboard to get PCI-E.
Correct.