How do you detect the main hard drive letter such as C: drive?

Question

Try

Path.GetPathRoot(Environment.GetFolderPath(Environment.SpecialFolder.System));

That will return (normally) C:\

But it depends on how you define the "main" hard drive. This will give you the drive Windows is installed on.

This should work (assuming you want the drive that windows is on):

string rootDrive = Path.GetPathRoot(Environment.SystemDirectory);

"SystemDrive" is the environment variable on XP that you want.

Environment.GetFolderPath(Environment.SpecialFolder.System).Substring(0,1)

Reference from here.

var d = Directory.GetDirectoryRoot(Environment.GetEnvironmentVariable("windir"));