jeez,...where do we start.....
here's the thing,..if you want to enhance system performance..ideally you'd want to change your mobo and proc.right?
but somehow,....you can never really enhance overall system performance,..given the old hardware that you have.
however,..a mobo and proc upgrade is still possible without changing any of your existing hardware.
but if you truly want your system to perform at its peak,..then you'd have to change those rams...are you using sdram stick?..if you are change them to ddr,..but this will depend on what your new mobo supports.
your existing graphics card will fairly do its job,..if you're not a gamer.but if you do heavy graphics work and gaming,..you'd want to get a high card,..a 64mb or 128mb.
your cdrw,..is still ok,...but to tell you honestly ,..its quite slow.
the rest of the hardware you mentioned,..probably won't affect system performance
so,..if you are planning to upgrade,..you should consider,..the mobo,processor,ram,graphics card and cdrw. this is just my opinion..
the final step is still up to you