Correct amound of Ram not recognized by Bios and Windows

Hello to all,
Today I received 1 stick of 2GB DDR2 Ram 800mhz I ordered a while ago. I tried to install the stick only to find out that Bios AND Windows only recognized 440MB out of the 2GBs they supposed to be! My motherboard is an MSI P31-Neo2 FR and the 2GB Ram stick is a samsung one. Now am definetely sure my motherboard supports this stick as there is no reason not to. So I reinstalled the 2x512mb stick I already had an now have 1.5GB of ram. I ve checked the bios and couldnt find anything for this problem. On top of that CPU-Z recognizes that stick normally and shows me that I have 3GBs of ram now!
Any ideas on whats going on? I can provide you with any more information or pictures if needed!
Thanks in advance

http://global.msi.com.tw/uploads/t [...] 0_1336.pdf

Lists the various modules that have been tested to work with your board.

No reason that you know about?

The Intel P31 chipset is a cut-down derivative of the higher-end P35 silicon. Cut-down meaning, some features or capability has been removed to make it less expensive. As such, P31 has more restrictions on supported memory technologies or configurations.

2GB modules must have the following specs:

# ranks: two (double rank)
# DRAM chips: 16
DRAM organization: 128Mx8 (1Gbit)

2GB modules of any other construction are not supported. Additionally, P31 supports a maximum of four DIMM ranks for all sockets/channels combined. To populate four sockets, all four modules must be single-rank. To populate two sockets, you could use:

- Two single-rank modules

*OR*

- Two double-rank modules

This assumes modules of the same type and construction. Mixed configurations are supported as well, as long as all modules combined don't exceed four ranks.

No, read again.

The sticker on the module, or other part numbers such as the markings on the chips, are the best information.

Also check for any BIOS updates for your motherboard. It just as well could be a BIOS issue.