Install Drive?

I know how to use the "InstallDir" to define a string for the install directory. But can I use something to find the drive letter?

For example:

I install my program into C:\anyfolder\
I can use the Get Parent function to define a variable as "C:" and then add to that as necessary. But what if I have more sub-directories. And I don't know how many levels down my users will install the program.

I need to be able to define the drive letter no matter how far down they put the install path.

C:\full\path\to\install\dir

is that what your talking about?

StrCpy $1 $INSTDIR 1 

This line code will copy the first character of $INSTDIR into $1. For example, if the $INSTDIR was "C:\Program Files\MyProg", $1 would be "C".

Be aware though that if the user selects a non mapped remote drive the first character will be "\".