>>The ISP technician suggested there is a problem with FastSite naming its folder including its name and "exe" file extension.<<
What version of FastSite are you using? I do not see an .exe extension on the folder name after using Add File in FastSite 2.1. Here are the paths that I see after adding the file tweakui.exe:
Are you sure that you did not rename the page after creating it? You can edit the page name to drop the extension (right-click on the page on the site tree, choose Rename).
"The place to go for help with Lotus SmartSuite"