1) Start any application say word or multiple browser etc.
2) While you r working on your process press CTRL+SHIFT+ESCAPE to open the Windows Task Manager and go to processes to see all the running processes . It will also show you the usage of your CPU and your RAM
3) Now switch to the applications you have opened and start minimizing them.
4) Now go back to the Windows Task Manager and see the usage.
5) You will find that the memory usage has reduced by great amount.
So minimize eash tab on which you are currently not working and you can increase the amount of available RAM by a substantial margin.