Win7 x64 System list 4GB as 2.99GB usable

First of all you probably have integrated graphics which captures part of your system RAM for its own use. That could be as much as 1GB. Then I believe there are Windows functions that need to reserve RAM whether you are running 32 bit or 64 bit. What 64 bit does for you is allow you to utilize MORE than 4GB of RAM.

I do understand that IGP and other OS features takes RAM, what I din't is that the value shown as "usable" is after deduction of the above mentioned values. I am a new Win7 user, from what I know, WinXP simply reports the total usable (incl IGP video ram and system features) RAM. Thanks!

I am not sure I understand your point in #2. First of all, you are not running WinXP.

Memory that is used by an integrated video system is not available to Windows and is not reported as such. A 64 bit OS cannot automatically use all 4GB, even if it is not in use by the video system. You have the same problem as in a 32 bit OS, that is a portion of the address space is shared with memory mapped hardware which must have priority. In a 32 bit client OS there is no solution, but there is with a 64 bit OS. To use all 4GB of RAM the conflicting memory must be mapped to a region above the 4GB mark. There is usually an option in the BIOS to do this. Since every system is different I don't know what it is called in yours.

I was a previous user of Windows XP WinXP - Reported Ram in System consist of both available, using, system reserved and graphic ram altogether. which differs from what u described of Windows 7, where the Usable Memory = Available Memory - System reserved - Graphic Ram.

According to M$ article HERE, this is expected behavior on computers that are running Windows 7 i_Xp/Vista/W7User