Child process error

Hi,

We have made a `node-windows` service that have a main script that run a child process command to open an .exe like this
```
var cp = require("child_process");
cp.exec("C:\\Users\\test\\Desktop\\file.exe", function(error, stdout) {
});
```
If we run `node main.js` it's work like expected, but if we run service it throw error
`Command failed` I don't know why.. Any idea?

Start with the child_process.exec call shown in main.js and reproduce the difference between running node main.js and running the same command as a node-windows service. Inspect the service execution context and the error returned by the callback; done means the cause of Command failed is identified and the executable behavior is explained or corrected.

Written by the indexing model from the issue text.