Hi,
Mine, as you can see, reserves only 321 MB
So, I would suggest you do the following:
1 - Open command prompt with administrator rights, and run the system file checker, use this command sfc /scannow, if everything ok, close command prompt.
2 - Windows key + R and type msconfig, go to boot then advanced options and set max. memory is 0 and unselected. Reboot the machine.
Check if worked, if not:
3 - Windows key + R and type sysdm.cpl, go to advanced tab | Performance Settings button | Advanced tab | Change button, there select and highlight C drive and set to no paging file & press Set button, click OK to apply. Reboot the machine.
4 - Next, when the machine is booted up, go back to sysdm.cpl and same location as before and this time select the check box at the top "automatically manage paging". Reboot the machine.
5 - Next, once the machine is booted up, check msconfig again and confirm that memory check box is still unchecked and set to 0. Reboot the system again.
Check if worked.
If it didn't work, you have to check within the bios setup, there must be a configuration that overrides Windows. Check if your settings for the internal video card are set to use way more than what is needed for example.