I'm trying to make a windows 7 bootable USB so I can use the repair function on it to repair a friends laptop but I'm having a problem with the file name that Sardu is asking for.

As you can see in the image above the file name it's asking for is "InstallWin7*.iso", the problem? I can't put a symbol in the name of the file. I've tried re-saving the ISO heck i've even tried tricking Sardu into thinking it was a different program that doesn't require a symbol in the name.
Basically I'm using Windows 7 and Windows doesn't like symbols in file names.
So my question is, how on Windows do I get it so the file name has a symbol in it?