Right click on the "My computer" icon on the desktop, click on "properties", the window that appears gives you your computer details including the memory installed. From there, click on the "performance " tab and it will tell you the amount of ram and how much resources free. Or download Rambooster 1.6 from here, click here. This will tell you what your free memory is and helps you optimize it. It's freeware. Good luck.
If you open rambooster it will tell you your cpu usage and how much free ram. Set the target level of ram and click on "optimize"If you then go to "edit" you can set it to optimize at whatever level you choose when it gets too low. However, on this computer I only have 128 ram ( IGb on my main comp so I notice a difference! )but this runs quite fast enough except when I play cd's as well which hogs the resources. What programs are loading and running when you start up?