load txt file in standalone from users c:/ dir

[mee]

I have a standalone application that runs from a CD. I have worked out how to use loadvariablenum to load and use variables in a text file using a relative path eg

loadVariablesNum ("testtext.txt", 0);

but need to know how I can specify an exact path (so it can look for the file on the users hard drive) eg

loadVariablesNum ("c:\\testtext.txt", 0);

this doesn't work can anyone tell me if there is a way to do it?

The reason for doing this is that we need to know what operating system a user is using as this alters what is installed from the CD - we have a program that detect the op system writes a text file to the users drive that I am then trying to read with Flash - If there is some way to detect the op system with a standalone flash system I would love to hear about it.
Many thanks
me