How and what can I upgrade my Pentium 4 SiS 645dx chipset to?

Question

I have a MSI MS-6547 1.0 motherboard.

Answer 1

That's quite a slow and outdated platform. Upgrading either just the processor or the motherboard would not deliver significant performance improvement. Consider this cheap upgrade that will do wonders to your PC:
Processor: Intel E2160 about $85
http://computers.pricegrabber.com/processors-retail-box/m/36344418/

Motherboards:
If you still want to use your ddr RAM and AGP card:
http://www.asus.com/products.aspx?l1=3&l2=11&l3=272&l4=0&model=1276&modelmenu=1

If you want the real upgrade to current ddr2 RAM and PCIe graphics interface;
http://www.asus.com/products.aspx?l1=3&l2=11&l3=182&l4=0&model=1494&modelmenu=2

Answer 2

It is a Socket 478 motherboard. It has a Front Side Bus of 400Mhz max. Socket 478 Pentium 4 2.0Ghz with 400Mhz FSB is about the fastest chip for this motherboard. There are socket 478 chips that are running at 3.2Ghz but, they have a 800Mhz FSB which your motherboard does not support. Here is a link to the fastest supported processor....
http://www.geeks.com/details.asp?invtid=P42000A478&cat=CPU