Windows 7 Home x64, just in case you add any extra memory.
Have you though of a light Linux install ?
No Linux. This is for my brother in law and his kids and wife. They are not technically inclined at all. Every piece of software they have is for Windows. I'm not about to open up that tech support nightmare. I have a key for Win 7 ULT, not Home. I thought for some reason Vista would be faster on this hardware then on Windows 7. Installing 7 now.