Recently windows has been only able to use 4GB of my 8GB total RAM (HTPC in system specs). When I go to Computer>properties it says: Installed memory (RAM): 8.00GB (3.99GB usable), so it knows I have 8GB installed, but its not able to use it. Windows task manager confirms that only 4GB is being used. CPU-Z and BIOS both say that I have 8GB installed, and CPU-Z lets me view the properties of each 4GB stick. I have gone into msconfig and set the maximum amount of ram to 8192MB, restarted, still at 4GB. I am running Windows 7 Professional 64 bit. Just not sure what to try next... Windows has been fine using 8GB on this system in the past, this only started recently. Thanks in advance!