I have an old HP server tc2120 with 4GB (4 1GB sticks) of physical memory installed running on 32-bit xp, not sure about the chipset and bios info. BIOS reports 2.9GB of memory, system property shows 2.87GB, and msinfo32 shows 4GB. I read about how xp could use up to 1GB, but BIOS should have reported 4GB, instead of 2.9GB. What could be the issue?
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Could be that one of the memory sticks is defined as spare in BIOS. That's part of the advanced memory protection function. Or one stick is dead. You should have system management software installed, that tells you that.