# Demo variables
$Path1 = '$env:windir\system32\windowspowershell\v1.0\powershell_ise.exe'
$Path2 = 'c:\chemin\inexistant\altf4formation.txt'

# File name with extension
[System.IO.Path]::GetFileName($Path2)
# Or (requires that the file exists)
(Get-Item $Path1).name

# File name without extension
[System.IO.Path]::GetFileNameWithoutExtension($path2)
# Or (requires that the file exists)
(Get-Item $Path1).Basename

# Just the file extension
[System.IO.Path]::GetExtension($path2)
# Or (requires the file to exist)
(Get-Item $Path1).Extension

# Just the drive letter
[System.IO.Path]::GetPathRoot($path2)
# Or (requires the file to exist)
(Get-Item $Path1).DirectoryName.substring(0,3)

# The path without the file name and extension
[System.IO.Path]::GetDirectoryName($path2)
# Or (requires the file to exist)
(Get-Item $Path1).DirectoryName