I also have this problem.
Win XP SP3. I just checked for PDF24 updates and am running the latest.
Works fine when installed, but after a restart I get the error message "The PDF24 Windows service is not started..."
Clicking on the "Start PDF24 service" button produces a "Run As" dialog and then nothing. The service does not start and I cannot start it from Windows Management.
Installed to default folder.
The service path to executable is "C:\Program Files\PDF24\pdf24.exe" -service
Any ideas how to fix this?