Have installation detect a drive for installation

[the_grove_man]

We have a requirement for a C drive or D drive installation for one of our programs. What I need the installation to do is if the installation detect a D drive that has a certain folder structure like so:

D:\AppData

If it finds it, it will install it there. If it doesn't find it, it will install it here:

C:\AppData

It is a .NET 3.5 program

[#2]

ExistsDir("D:\\AppData");

[the_grove_man]

Thank you.