So after speaking with the network guru where I work, this is apparently a well known issue that has occurred on many different systems (from his experience).
I bought a Dell Studio desktop some years ago now, which I am still using as a main desktop PC. It has a Broadcom inbuilt NIC. A few days ago, I switched it on as per usual, and noticed an email come in on my ARPWatch daemon I have running on my Linux broadband router. New station, mac address: 00:10:18:00:00:00
Turns out that the Broadcom NIC in the Dell has lost it's original MAC address. In fact, running DOS diagnostics, it reports the MAC address now on the card as completely invalid. So what is now happening is that when Windows 7 starts up, the NIC driver looks at the card, sees no valid MAC, and assigns it with a default of 00:10:18:00:00:00 - what a PITA !!!
I can of course set the MAC back to what it was through the Windows 7 NIC driver (which I have done) - but does anyone have any pointers as to how to properly re-write the MAC address back onto the NIC itself? Or is this pretty much a case of - another PITA technilogical glitch that's (a) non fixable and (b) too weird for even Dell technical support monkeys to appreciate and diagnose?
PS - I note from a Google search that this same issue has surfaced on Apple MacBooks: https://discussions.apple.com/thread/2641278?start=0...