Windows 7 detects only 3GB when 4GB is currently installed
Windows 7 detects 4 GB (2.94 GB usable) of installed memory.
For 32-bit versions
32-bit version of Windows can not manage more than 3GB of RAM For more information: http://ccm.net/faq/1571-why-windows-is-not-detecting-the-4-gb-of-ram-installed
For 64-bit versions
Most of the recent motherboards (less than 4 years) can manage more than 3GB of RAM. If your PC is unable to handle more than 3GB of RAM it is probably due to an incorrect BIOS setting.
- Open the BIOS.
- Go to Advanced > North bridge Chipset configuration > Memory remap feature > Enabled.
You also need to perform the following operation:
- Click on Start > Run .
- Type the following command and press Enter: msconfig
- Go to the Boot tab and click on the Advanced options button.
- Check "Maximum memory" and adjust your settings.
For PCs with and integrated GPU
- Integrated graphics chipsets use the main memory of the PC as video memory. This amount is deducted from the total memory.
- E.g a 64 bit OS: 8.00 GB (6.20 GB usable) because 1.80 GB is used by the graphics chipset.