Long before mobile smart phones, truckers were using apps like copilot gps on their offline laptop for just this. I used to have it on a laptop for install work I did. In fact, I continued using it in areas with no cell coverage. Another app I used was Microsoft Streets and Trips. In 2006, they added a GPS version that did turn by turn nav.
That said, the point still stands. I did some searching, and Streets and Trips are discontinued. Copilot was bought by Trimble and AFAIK, you can only get the mobile app versions (they still have offline support). I think their truck fleet software will still run on laptops, but are sold as part of a bulk purchase.
I did find MapFactor, which I've never used, as being something that will work on Windows and Linux (via wine) and it provides real-time GPS navigation.
There are still more than a few great turn by turn navigation libraries that run on ruggedized windows tablets. There were two that escape my mind.
Quite often they work completely offline, and also cover more information related to topography and driving routes that may not be traditional roads on existing maps. For example, the path to a location in a farmer's field, etc.
As a programmer with serious mobile experience I fully understand it. But it sound a bit crazy that a powerful and more superior (and open! In both hard and sometimes soft - if with an opensource OS) platform need so _emulate_ an embedded one (mobile, usually at least partially proprietary one) to provide turn-by-turn nav: what appears to be a first-order need of anyone in the modern world.
I used to have a pink netbook that ran Microsoft Streets and Trips that I used together with a Bluetooth GPS. I had a power adapter that plugged into the cigarette lighter of the car and also a line in cable for the stereo. I could play music with Windows Media Player and have turn-by-turn directions work flawlessly. It was particularly good for road trips with a navigator in the passenger's seat as it had a great user interface for managing large numbers of points of interest and making routes that hit multiple points. It was the best satnav I ever had.
I remember the time I was heading south from Syracuse in an area notorious for state police speedtraps when I had pulled alongsides a greyhound and my son had logged into the WiFi on board the bus. The bus driver got pissed at us and got up to 95 mph to shake us. I gave up first but I figured he'd have a lot more to lose from getting a ticket than I would.
The bus driver probably didn't know or care about the wifi, just this car that kept strangely in pace with him. Maybe the driver thought OP was going to intentionally get in an accident for some insurance scam.
If your laptop has 3G (or better) radio, it has also positioning bundled in.
However, although the devices might run on ancient stable standard, but that does not mean, that operating system is not playing silly games there. If you had an app that talked to them via serial port, you could throw it away once Microsoft introduced GNSS subsystem.
iPad is super handy but I'm not sure a laptop has turn by turn nav, maybe it could via an emulator.