There're thousands of add-ons on the Web for the classic FSX and Prepar3D v1 to v3. Take off from anywhere in the world, flying some of the world’s most iconic aircraft to any one of 24,000 destinations.
No need to worry, you can rest assured that It's simply a false positive detection by the anti-virus software. My Avast anti-virus, is doing exactly the same. For some reason the scanners are unhappy with the .exe installer file that is provided in the scenery folder. I've noticed this happening quite frequently with Avast since they updated the software a couple of months ago. The software is now overly sensitive, with many files that are completely harmless! I suspect exactly the same problematic issue with AVG.
Anyway hope that reassures you. You simply need to disable your live AVG scanning for 10 minutes or so, to happily complete the installation. The Sardinia scenery very good, IMHO well worth adding to your sim. All the best.