Hi,
when you have to eject or unmount DVD iso from your VMs, may be the iso files resists on datastore you want to remove, these one liner should help you.
This ejects all DVDs or CDs from your VMs
PS D:\> get-vm|Get-CDDrive|Set-CDDrive -NoMedia -Confirm:$false
This ejects all DVDs or CDs from your VMs where the iso files are at datastore0
PS D:\> get-vm|Get-CDDrive|?{$_.IsoPath -match "^\[datastore0\] .*"}|Set-CDDrive -NoMedia -Confirm:$false
Or for a specific VM
PS D:\> get-vm "yourVM"|Get-CDDrive|Set-CDDrive -NoMedia -Confirm:$false
Michael