BIOS wont detect 4GB RAM

Here are my specs:
AMD x2 4200 overlocked
2GB Corsair and 2GB Kingston Ram (4x 1GB)
Asus A8N SLI SE now changed to MSI RD480 Neo 2 Motherboard
1 Samsung spingpoint SP2504c Sata 250GB
1 Samsung Spintpoint HD401LJ Sata 400GB
Antec Truepower 550w PSU
Artic cooling Freezer 64 pro
ATI sapphire 4890 OC edition
NEC 4570A DVD-RW
Windows 7 ultimate 64 bit
startech sata 2 controller

A few months ago the Asus motherboard broke, i was able to use 4GB ram on 64 bit windows 7 without any problems on the Asus. I then repalced the motherboard with a MSI RD480 NEO 2 which claims to support 4GB RAM and installed windows xp. A couple of days ago i then install startech sata 2 controller and windows 7 64 bit and noticed it did not detect the full 4GB ram but CPU-Z was able to detect 4GB after googling i noticed theres a feature called memory remapping, There is no option in the BIOS to enable it however in the windows 7 resource monitor it shows the installed ram and as 3GB and hardware reserved as 0MB. Today i noticed in CPU-Z detect one of my RAM as 320MB i moved the ram to different slots and it seems to be ok again, CPU-Z is detecting 4GB BIOS still detects 3GB. MSI motherboard http://eu.msi.com/index.php?func=p [...] &cat3_no=6

cpu-z at one point detecing one of my RAM as 320MB http://i67.photobucket.com/albums/ [...] yissue.jpg
Just got a reply from msi with links to a new bios, now flashed to version 3.34
Any help is greatly appreciated.

update:
This new BIOS ruined my pc, it kept having BSOD, the blue screen code was video related so i went into safe mode and disable the ati graphics driver, at this point windows 7 detects the 4GB and post screen detects 4GB but not the BIOS, I restart the pc and windows 7 automatically installs a new driver and it bsod again. After i reset from a BSOD or hang it fails to boot, lights flash no display. When i reinstlall windows 7 it just blue screen contstantly and after each time i have to clear the cmos. So at this point i dont have a working operating system due to constant crashing and bsod. It has now gotten to a point where i cant be bothered to fix it anymore and going to wait till i have money to build a new one.

update:
after several tries of installing windows 7 i then tried windows xp 64 bit edition, which installed fine no bsod and it is able to use 4gb no problem however the booting up problem after reset still remains, should i revert back to the previous bios?

hey, can you share the v3.34 bios please? i'll really apreciate it