If you are running a 32 bit OS such as win 7 32 bit then you have way too much ram.
If you have a 64 bit OS such as win 7 64 then you have plenty of RAM.
I run a 8 gig RAM Win 7 64 bit with an I7 processor and have never run out of memory.
Rendering time is near instant for 3D cnc files and smoking hot fast for RIP files.