How to get the most out of upgrading RAM on PC?

[shanboy]

I have a pc with intel core 2 duo processor 2.8 Ghz and 2 GB DDR2 SDRAM 400 MHz and my motherboard is Intel DG41RQ .OS i'm using is Windows 7 Pro.

i recently added one more RAM module of 2 GB with same frequency.
I find that after adding RAM,it shows 2.96 GB usable.
Why is it so?
What's the logic behind it?
What all needs to be considered before going for an upgrade to get maximum out of it.

Any Guidance / help is greatly appreciated

Thanks

[Rabbit]

You have a 32 bit processor and OS. The theoretical maximum is 4 gigs on a 32 bit system. However, it is impossible to achieve the theoretical maximum because the rest of the hardware needs address space as well so the amount of usable RAM on a 32 bit system is going to be around 3 gigs.