RjBass:Core 2 is the name of the actual core series and has nothing to do with how many cores are in the CPU. Since solo means 1, then they called the CPU Core 2 Solo meaning that it is built on Core 2 technology but only contains 1 core. Hence the reason why a Core 2 Duo has 2 cores and a Core 2 Quad has 4.
A little contradictory but I think it's just a stupid marketing scheme with "longer battery" life slapped onto it. You want two, you might not think so but it's super handy for newer OSs and some programs.
Reasons to get Windows 7:
Snap to maximize windows
Formatting huge hard drives
It's Vista but better
The ASUS M4A78-E sucks, don't get it.