Meh.
The machine on my desk was built in 2007. It's 2013.
It's had the drive subsystem upgraded, two video card upgrades and one processor-and-RAM upgrade (chip replacement to go from quad-core to hex.) It has also outlasted two sets of monitors and currently drives a 4-way array of monitors that look like something out of the Starship Enterprise.
It had Windows XP on it and was upgraded to Windows 7, which it currently runs.
There is no Mac path that would have permitted this, and there is utterly no reason for me to replace it. With the Hexcore CPU in it (i7) I can't come up with a reason why I'd materially change it in the foreseeable future, and those upgrades were comparatively cheap too -- none was more than $250 other than the CPU (which was a bit nasty in price, but heh, it is what it is; I re-used the QuadCore in a machine I built for my kid.)
there is only one mother board on the market that can do run both OS. 

