Please refer to the below links.
http://support.microsoft.com/kb/929605/en-us
http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/in-windows-7-have-4gb-ram-but-only-275-gb-usable/18bdbb32-a654-e011-8dfc-68b599b31bf5
Thanks for using 3DP Chip.
Please refer to the below links.
http://support.microsoft.com/kb/929605/en-us
http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/in-windows-7-have-4gb-ram-but-only-275-gb-usable/18bdbb32-a654-e011-8dfc-68b599b31bf5
Thanks for using 3DP Chip.