How can you eliminate the possibility that an application error is caused by another application or service running in the background?

a) Run the application in safe mode with networking, if it runs normally it's not the app but might be a conflicting application.
b) If the application works in Safe Mode, then you can assume the problem is not with the application, but with the operating system, device driver, or other applications that load at startup which are conflicting with the application.
c) Windows setup DVD, select Repair your computer, select the Windows installation to repair, the System Recovery Options windows appears, click Windows Memory Diagnostic tool.
d) The file association between a data file and an application is determined by the file extension. A program associated with a file extension is called its default program.