You could go for this, free upgrade to 7
http://www.newegg.com/Product/Produc...82E16832116677
Or just use the RC for now, free
http://www.microsoft.com/windows/win.../download.aspx
Overclocking the 945, you use the bus. Just start raising it a few mhz. till it gets unstable then back it off a few. If you want to go higher, you will have to bump up the CPU voltage. If you do raise the voltage keep a eye on the temp.
When you use the bus to overclock the memory speed will increase, so you will have to raise the memory voltage after a point. Or you can just bump back your memory speed, say if your runing DDR3 1333, just set it back to DDR3 1066. After raising your bus you can get your memory back close to it default speed.