Here are the steps for you to follow on a Windows 7 PC:

1. Right Click to My Computer
2. Click Properties
    
   

   Step 1 and 2

3. Click Advance System Settings
   

   Step 3

4. Enter password if ask for Administrator Password
5. Click Advanced Tab
6. Under Performance Click Settings
    
   

   Step 5 and 6

7. Click Advanced Tab again
8. Under Virtual Memory Click Change
   

   Step 7 and 8

9. Remove the check from Automatically manage paging file size for all drives
10. Select a drive, ea C:
11. Click the Radio Button Custom Size
12. On the Initial size (MB) input atleast 500
13. On the Maximum size (MB) input as much as 1024, 2048, 4096, 8192, or even 16384
14. Finally Click Ok and accept Restart Your Computer if required.
    

    Step 9 to 14

    Thank you to this site for sharing this steps, I just modified the steps and add some screenshots all credits remain to the said author.

    Here is my RAM now! 9GB!

    

    My RAM 9 GB! Or Should I say Virtual Ram!