Some friends here on the Hyper-V team shared a PowerShell 2.0 script for getting a list of VMs:

# List VMs

$vmList = gwmi -namespace root\virtualization Msvm_ComputerSystem |`
    where{$_.Name -ne $env:COMPUTERNAME}

$vmList | select ElementName,Name,EnabledState,StatusDescriptions | format-list

For more info on how to use PS cmdlets see:

See also James O’Neil’s New and improved PowerShell Library for Hyper-V. Now with more functions and... documentation!

For all 35 sample Hyper-V PS1 scripts in a zipfile, go to: Hyper-V PowerShell Example