Can i use DDR2 ram in my toshiba laptop which has DDR earlier ?

Answer 1

So long as the mother board and slots supports it, Yes - although you may need to update your drivers. Just make sure you replace ALL the RAM sticks, as they all need to be the same speed.

Older model won't support both, but newer models can take either - if in doubt check with Toshiba in regards to your exact model

Answer 2

Newer models cannot take both, they fit in different size slots anyway. You wouldn't even be able to physically put the DDR2 in the DDR slot, so the answer is no.

Answer 3

Never use DDR2 in DDR slot, it will damaging your DDR2 .