[Question?] Windows XP not recognizing all 4GB memory

I built my own computer, with the spec's below. Windows XP does not recognize (or at least display in system info) all 4GB memory, but only 3GB. I know both memory modules are good...just tested each one in computer solely. Any idea why?

Windows XP MCE 2002 / Fedora 12 (32-bit)
Biostar VIA P4M900-M4 motherboard
Intel Celeron, Socket 478 Pentium 4 - 2.6GHz
nVidia XFX GeForce 8600 GT video card
Sony CDRW/DVD CRX330E
NEC DVD+-RW ND-3530A
Samsung 250GB Primary IDE HDD
Samsung 40BG Secondary IDE HDD
Kingston 4GB DDR2 Memory

Nevermind, found the answer here:

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Enjoy All,

Now that forums where able to solve the problems for you I will now close this Post..