To speed up your windows or to increase RAM virtually,

>>Right click on My Computer
>> Properties
>> Advanced
>> Performance - Settings
>> Advanced
>> Virtual Memory - Change
Keep the initial size same as recommended and maximum size double of it then restart your system.
It will improve speed of windows and you can play some games which require higher RAM.

When a window is active, press the F11 key of the keyboard to get the biggest window possible and press F11 again to restore it.