One of the first things you need to do is ensure that you know the GPS is functioning and how to access it. I would suggest two utility programs for doing that.
The first is GPSGate. This program will find a GPS if it's installed and activated and functioning properly. When you run it it puts an icon in the System Tray. To find your GPS you right-click the GPSGate icon, select Settings and click the Settings Wizard button. GPSGate will tell you where it found the GPS. The System Tray icon changes colour to tell you if it has found a GPS and again when the GPS has a location fix.
The second is
Compass. It allows you to see what the GPS is doing. It's actually a neat application in itself but probably not useful for your client. It's a great diagnostic to allow you to see what the GPS is doing. This goes to your question about performance issues when the GPS is built in. You'll be able to see how many satellites the GPS sees and their signal strength as you place the laptop in different locations.
There is a wealth of information on here about the various nav programs, including reviews and also many useful threads that start out with the same question you asked. The Search function on here uses Google so it's quite helpful. And if you scroll to the bottom of this page you will see a list of similar threads.
If you're a professional and charging your client for this work you already know that the first thing you need to do is find out what sorts of things they think they want to do with nav software. Without that information, the only answer to "Which nav program?" is that any of them will do all the basic nav functions just fine.
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