That doesn't mean you can fix this. I too had a run in with over 2GB on the AMD 3700+ machines. I won't go over the boot.ini settings or registry entries to limit RAM but this is a well worn area except when it comes to this CPU and that much RAM.
Good luck with the BOOT.INI and registry settings. If this was a fresh install you would not see those settings as an issue. But some run registry cleaners and I can't explain why those add that.
But here's a nugget. CPU-Z can report the actual stick sizes and NOT what the system can use. You could lose a lot of time on that and I can only share that you won't be fixing that to report more than 2GB on the AMD 3700+ on most systems.
Again, the BIOS is your clue here it's the usual chipset limitation. If this must be fixed, change the chipset.
Recently upgraded my CPU from athlon 64 3700+ to Athlon FX55.
Motherboard is Asus 8Vdeluxe (rev 1.xx)
With the 3700+ (which I believe only supports single channel memory) the full 3gb (2 x 1gb sticks & 2 matched 512mb sticks, all PC3200) installed showed correctly in the bios and My computer/properties, and cpu-z as running single channel.
Installed the FX55, nothing else changed, and the bios and my computer/properties both show 2gb, while cpu-z correctly reports the 3gb as running dual channel.
I've tried every possible combination of ram size/slots/channels, with very varied reported sizes - cpu-z is always accurate in what it reports, but the bios is inconsitent.
The only thing I can see that may be causing this is that one of the 1GB sticks is generic and shows 3 JEDEC frequencies, whereas the other 3 all just show the 200mhz
I've tried lots of different settings in the bios (version 1018.002)but nothing seems to make a difference. Machine runs very well and quite a bit faster, but I'm starting to see page file usage & delays, and I'd like the full 3gb to be used.
OS is XP pro SP2.
Any ideas will be gratefully received.