Troubleshooting guide
How to fix the problem
In Windows 11 File Explorer, select View > Show > File name extensions. In Windows 10, the corresponding option is in the View bar. Extensions help distinguish a document from an executable file: .exe does not in itself mean a virus, but do not run a file from an untrusted sender, such as account.pdf.exe.
If the problem persists
Check the result with a file of a known format. Changing the end of the name does not convert the file to another format; if you get a double extension like .pdf.exe, don't run the file.
Request a repair