Haven't yet upgraded your home PCs to Windows 7? I can understand why: a single upgrade license retails for $119.99, which I find exorbitant for an operating system--even one as solid as Windows 7.
As you may recall, about a month ago, Microsoft rereleased the Windows 7 Family Pack, a three-PC upgrade edition of Windows 7 Home Premium (32 bit or 64 bit, your choice). The price: $149.99. That's a little more like it.