critical problem in computer? help need

[surya_sapui]

dear guys, i have asus k8n mobo, and 2.00ghz processor. ram 3 gb.550w smps.x1550 gpu agp.1 tb hdd sata.i see when i install 3 gb of ram then in bios show only 2.46gb of ram & in os (windows 7) it show 3.00gb(2.47 ram usable),i cant understand why it show like this.i see this, this kind of error in other pc when there 4gb or ram it shows 3gb something.but here i install 3gb & when i install 1gb then in bios show 400Mhz speed but when 2gb then 333mhz then i install 3gb then 200mhz show pls explain where is the prob, is there ram problem or mobo prob.

[hell_storm2006]

Check your BIOS. Maybe your default graphics driver is set to default which is on board AGP. Also your RAM's are of different frequencies so the higher RAM gets down-clocked to the lower frequency!