Appcompat.exe by Leo A. Notenboom Appcompat.exe was Windows 2000 tool that was used to fake the version of Windows for some setup programs. What is Appcompat.exe? A Windows 2000 tool (supposedly no longer needed in Windows XP) that used to fake the version of Windows for some setup programs. Become a Patron of Ask Leo! and go ad-free! Please note: appcompat.exe and appcompat.txt are two completely different and unrelated things. Subscribe to Confident Computing! Tech problem solving & safety tips & a weekly confidence boost in your inbox every week. I'll see you there! Slow Computer? Speed up with my special report: 10 Reasons Your Computer is Slow, now updated for Windows 10. NOW: name your own price! You decide how much to pay -- and yes, that means you can get this report completely free if you so choose. Get your copy now! Related Posts How do I resolve my problem with appcompat.txt? - Here's what to do when you see appcompat.txt. How Do I Fix Windows Update? - Windows Update can get confused or stuck. I'll review ways to fix Windows Update, including what I refer to as the "nuclear option". How Do I Reformat and Reinstall Windows? (XP & Vista) - Sometimes the best approach to resolving an issue, be it a virus or simply software rot, is reformat and reinstall. We'll review the steps. What are alternate data streams, and are they a security risk? - Alternate data streams are a little known and little understood feature of NTFS that allows information to be effectively hidden within other files.