Yep, then go for a socket AM2+ looking at a new one as I type abit AX78 deluxe (never used an abit board before.

SLI, AMD 770 chipset, etc. An AMD Phenom FX would do it justice I think.

Offcial line is : Change of mobo means new copy of Windows UNLESS you have a full retail version.

If your copy is OEM, then unless you can persuade Ms that your mobo "Blew" (and I'm not condoning this practice) then you would be faced with buying a new copy.

This would be a bit daft IMO now, as Vista is firmly with us.
If you buy a mobo / cpu bundle from the likes of Novatech, you would be able to buy a copy of the OS with it.

You could, although a) most of the higher end boards come with high defenition 7.1 surround sound onboard. And b) Creative have big driver issues with Vista.

The onboard sound these day's has come a long long way. I don't buy soundcards for my own machines anymore. This one would plug into my Pioneer home theatre system if I could stand the wellie it produces.

Instead, I use a set of 5.1 surround speakers that I've had for years.....More than enough.

You will need to have @ least 2gb DDR2 or DDR3 ram (the 2 types need different boards to use) and as you correctly say a new graphics card or pair of them if you go down the SLI route.

Fast HDD's 250GB+ (2 is better than 1)

Other stuff like keyboard, mouse, monitor you already have. Remember that power supplies are critical to your build, and the more graphics power you have, the bigger the PSU needed. The new PCIE cards require extra power, drawn straight from the PSU via special connectors.