I've been unable to install the newest version (1.8100) on 2 different computers, getting the same error msg:
"Error writing"... HeroDesigner.exe
The newest version of .Net is on the computers.
If you have Mids' opened, close it, and make sure you run the installer as an Administrator. Those are the two best guesses. :P
We've been seeing this a lot, and usually it's a permission issue. Make sure when you run the installer to right click it and select Run As Administrator. If that doesn't work, try installing Mids to something besides C: Program Files.
Luckily, the upcoming I19 release is going to automatically require administrator privileges, so we can hopefully stop seeing this bug.