Try:
public static Regex regex = new Regex(@".:\\Users\\.+?\\", RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled);
...
string result = regex.Replace(InputText,"");
If you are going to use regular expressions, get a copy of
Expresso[
^] - it's free, and it examines, tests, and generates regular expressions.