The Test-Path command may be used to test for the existence of a specific item under a drive:

Test-Path HKLM:SoftwarePublisher 

Test-path distinguishes between item types with the PathType parameter. The container and leaf terms are used across providers to broadly classify items.

When working with the filesystem, a container is a directory (or folder) and a leaf is a file. In the registry, a key is a container and there are no leaves. In a certificate provider, a store or store location is a container and a certificate is a leaf.

The following commands test for items of differing types:

Test-Path C:Windows -PathType Container 
Test-Path C:WindowsSystem32cmd.exe -PathType Leaf 

The Test-Path command is often used in an if statement prior to creating a file or directory:

if (-not (Test-Path C:TempNewDirectory -PathType Container)) { 
    New-Item C:TempNewDirectory -ItemType Directory
}