If it can't handle more than 704MB I'd say you made a bad choice buying your motherboard. Most boards sold today can support up to 4Gigs, although I don't see why any home user would need that much.
Check your manual, or the manufacturers website, although I'm almost certain you don't have anything to worry about.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w