I have an external USB drive that I use for backups. The backups are performed by a PowerShell script. My problem is that the drive letters change frequently, as other USB drives are plugged in and unplugged.

I updated the PowerShell script to determine the drive letter based on the volume name, which does not change. Here is the code that does this:

function GetDriveLetter($volume_name)
{
$drive = Get-WmiObject win32_logicaldisk | Where-Object {$_.VolumeName-eq $volume_name } | select -ExpandProperty DeviceID

if ($drive -eq $null)
{
Throw "Cannot find drive with volume name of " + $volume_name
}

return $drive
}