i installed 8 gb of ddr2 ram and its only showing as 3gb usable and in resmon 5gb is hardware reserved ive done the msconfig advanced boot option so theres no ram limit but its still the same theres no option in bios for memory remapping that i can see its 64 bit os the machine is a philips hepc 7602/05 bios is phoenix technologies,LTD 6.00 PG, 18/06/2008

Your PHILIPS HEPC system is not a popular item in the US & it would have been much helpful if you had supplied your full system details in your OP. Windows 7 News!

Are you sure the system is running Windows 7 64-bit. The 3GB limit you are seeing would lead me to suspect the 32-bit was installed. What information do you see when selecting System properties from the Computer window? Richard

you can check in resource monitor, under the memory tab, there you can see how much memory window see's and what it uses it for, my system has 4 gigs installed,shows 3120 available, but shows 879 reserved for hardware, this is not shown, although i cannot see it using 4+ gigs for this, i suspect that your mobo is not seeing all 8 gigs, which maybe because its limited to either 4 gigs or has a problem, or a bios setting is not correct, you could try reset to default on the bios, see if that works. right click my computer/manage/performance/open resource monitor/memory i hate computers! but cant help myself....