Comment 9 for bug 1456183

the output file should be in the same directory where you were when you ran the command. When you run this command, it will convert the file input.ps into the file output.pdf. The assumption is that the file input.ps exists and output.pdf will be created.

If it is not in that directory, it may have been automatically relocated by Windows for security reasons. For example, on Windows 7, if I run this command from the root directory C:\ then the output gets relocated to the directory:
C:\Users\Alvin\AppData\Local\VirtualStore\output.pdf. If your file has been relocated like this, perhaps that is the source of the problem with Inkscape as well. However I don't know why that would affect your machine and not mine.

In any event, you might try running Inkscape as an administrator and see if that helps. Do a right click on Inkscape in Windows Explorer and choose the option Run as Administrator, and then try the ps input.