The amount of RAM should be fine but a better video card will help.
But your computer shouldn't really be struggling. Have you cleaned the dust out of it lately?
Do you have enough cooling?
You may want to check the temps. Use a program like HWmonitor to check them out.
Just for reference, my 2nd computer is
6 GBs of RAM
Nvidia GTX 260
and it didn't have any problem playing Witcher 1.