Want to upgrage my processor

Hello,
i have an AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ 2.00 GHz......and i would like to upgrade but am not sure what i can upgrade to.....im running windows vista home premium 32 bit operating system with 3 gigs of ram and an NVIDIA GeForce 8600 GT video card.....when i go into the windows experience index i get a 4.8 on the processor while i get a 5.9/5.9/5.5/5.7 for RAM, Graphics, Gaming graphics, and Primary Hard Disk....so i would like to upgrade my Processor but i have no idea what i can get....