Windows was available in Nebraska. This commercial is a parody of other commercials that, for legal reasons, had to exclude Nebraska. That line in this commercial is a wink and a nod to that.

So what was up with those commercials being parodied?

Prior to 1991, all 800 numbers were carrier-specific. Because of the mixed-up telephone system the US had after breakup of Bell, this meant that to call from one side of the country to another (such as on an 800 call), you may have to cross several carriers. This could get expensive.

To limit this, companies with 800 numbers got wise and centralized in the middle of the US. Due to its central location, Nebraska ended up the destination of many call centers for the, on average, cheaper 800 call rates. So companies moved their call centers to Nebraska for financial reasons.

But why did that make offers void? Because this 800 system could not successfully route in-state and out-of-state calls until 1981, when AT&T developed the tech to do so.

So throughout the 60s, 70s, and early 80s, the offers were void to Nebraska callers because they literally could not make the phone call.

As dumb as this sounds, remember: until the government stepped in in 1983, phone companies wouldn’t even allow consumers to own their own phone!

As an aside, there are still a lot of call centers in Nebraska, but the restirctions on 800 numbers being loosened has created a long, slow exodus of such jobs.

Refs: https://www.ringcentral.com/blog/the-history-of-800-numbers/amp/

Edit: a court mistake.

Phone lines used to be controlled by a Bell monopoly. Nebraska is the home of the Stategic air command and they insisted that they had a bunch of lines available to them due to the cold war. So Nebraska had a lot of phone lines that no one was using because Nebraska isn't very populated.

Bell had a rule that 1-800 numbers couldn't be used for in state and out of state calls. So because of the surplus lines and low population companies opted to sell our of Nebraska because they wouldn't be losing out on much in the way of sales. Most Nebraska based 1-800 numbers decided to just say that offers weren't available in Nebraska instead of having a second number just for the state. These numbers required subscriptions that were payed monthly and had slotted amounts of minutes to use and overage fees.

The ad doesn't have a 1-800 so Balmer wasn't being serious as the whole ad is a joke playing off 1-800 product ads of the time. Most people would just go to an electronics store and purchase windows.

Give me a few minutes to dig up sources. I have them they are just not on me right now.

Edit: my source texts aren't in my office and must be at my parents house. I'm searching Amazon for the books but I understand if the mods have to remove my comment.