My computer has 4GB of memory but only show me that it has 2 75 G

[Guest]

My computr has 4 G of memory but only shows me that there is 2.75 ?
Also my dvd player is pluged in to to the mother board harness but it will not play dvd or cd?

Can some body help me?

 

[aford10]

A 32 bit OS is limited to ~3.25GB of memory. The rest is likely reserved by the system.