All 32bit operating systems can see a maximum of 4GB. It is a mathematical limit, not the OS. Vista x86 like XP x86 will show a little over 3GB on System Properties. This is normal. The "missing" ram is not really missing It is used by the system and not presented to the user. There is a range of addresses at the upper end of 4GB that is reserved. In a system with less than 4GB these are logical addresses and are handled by the system that way. However, when the system has 4GB it must block out physical ram to protect the reserved addresses. In addition, the BIOS will reserve some additional address space for use by devices detected by the BIOS.