32 bit OSs have a max of 4GB minus whatever other components you have that use memory (as all memory needs to be mapped). The official barrier is 4GB, however the real-life barrier depends on what other hardware is in your system. to answer the OP question, no, windows is only using 3.25.
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CPU || e8400
RAM || 4GB corsair xms2 pc6400 800mhz
HDD || 2x WD Raptor 150GB 2x WD 500GB
MBO|| EVGA 680i SE
GPU || Evga 8800GT Superclocked w/ Accelero
PSU || Silverstone 750 watt
Case|| Antec p182
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