[H] Question about Windoes 10 media.

[DSinc]

I am not out of patience, but I wonder whether MShas forgotten me. I 
still have 3 machines on
my network still waiting for the Win 10 fairy. If ever?
so far only "Wal-Mart" and "Amazon" have popped up as retailers with 
product. I'll choose
"Amazon." (Win10 Pro "System Builder OEM, $126.00) for my last WinXP unit.
What exactly is a "System Builder OEM version??
Best to you and yours, and Happy Gobble Gobble!!
Duncan