you caN Always buy windows 7 and put it on
Something to watch out for on newer hardware.
Stock Win7 is now rather old -- the latest SP1 install CDs are from 2009. As a result, it is common that when you bring up Win7 on new hardware:
But since you don't have any networking yet, and might not have USB, it can be a bit challenging to get the drivers onto your new Win7 installation. Some investigation may be required to find the chip maker's VendorID (VID) and ProductID (PID) values from the Windows Device Manager utility.
I've done all the above. It's certainly possible. But it's time-consuming and requires patience and full knowledge of device driver installation.