It's a Bug with 10.40/41 Installer.exe that manifests with Windows XP. * See Ben's Comments: Installer says Entry point not found http://forums.x-plane.org/index.php?showtopic=89546 From: "Ben Supnik" <ben@x-plane.com Sent: Thursday, October 15, 2015 10:10 PM Subject: Re: Bug report: Can't update to XP-10.40/41 on Windows XP Machine Thank you for reporting this!!! This is a bug in the installer - the defect was fixed in X-plane itself but did not make it to the installer. We should have a fix for this sometime next week; as soon as I have a fixed installer I'll send you a copy to test - that will let you update! cheers Ben When X-Plane came out (a while back now) Nov-Dec-2011, LR promised that X-Plane 10 would be compatable (run on) with Windows XP for the Life of X-Plane 10.. But a lot has changed since then: X-Plane gone 64bit, Windows 7, 8/8.1, and now 10 Support for Widows XP just has to take a Back-Seat with where we are Today - it may have gotten just "too hard to do" ! Not sure what the next X-Plane 10 release will be (10.42+), but 10.50 will be a Biggie. Let's cross our fingers and see if LR can keep it's Windows XP Promise in the Future.