Here's a copy of a script I was using to clean XenTools from XenServer 6.0 I believe. Please include all the reg keys and files mentioned. Thanks!

$appName = 'Citrix Tools for Virtual Machines'
$appFileName = 'uninstaller.exe'
$appParameters = '/S /NORESTART'
$appSourcePath = "${env:ProgramFiles(x86)}\Citrix\XenTools"
If (($ComputerManufacturer -ne "Xen") -and (Get-InstalledApplication -Name $appName))
{
    Write-Log -Message "Uninstalling $appName ..." -WriteHost $True -LogType 'CMTrace'
    # http://discussions.citrix.com/topic/347782-unable-to-installuninstall-xen-tools
    Execute-Process -Path "$appSourcePath\$appFileName" -Parameters $appParameters -CreateNoWindow -PassThru
    Remove-Folder -Path "$appSourcePath"
    Remove-File -Path "$env:windir\System32\xennetco.dll"
    Remove-File -Path "$env:windir\System32\drivers\xen*.sys"
    Remove-File -Path "$env:windir\System32\drivers\scsifilt.sys"
    Remove-File -Path "$env:windir\System32\drivers\xevtchn.sys"
    Remove-RegistryKey -Key 'HKLM:\SOFTWARE\Citrix\XenTools' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\xenvbd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\xenvif' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\xenvbd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\xenvif' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\xenvbd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\xenvif' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\Citrix Xen Guest Agent' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xenbvd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xeniface' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xennet6' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\Application\xensvc' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xenvif' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\System\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\System\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\CurrentControlSet\services\eventlog\System\xenvbd' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\Citrix Xen Guest Agent' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xenbvd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xeniface' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xennet6' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\Application\xensvc' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xenvif' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\System\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\System\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\services\eventlog\System\xenvbd' -Recurse

    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\Citrix Xen Guest Agent' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xenbvd' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xeniface' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xennet' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xennet6' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xensvc' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\Application\xenvif' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\System\scsifilt' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\System\xenevtchn' -Recurse
    Remove-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet002\services\eventlog\System\xenvbd' -Recurse

    Set-RegistryKey -Key 'HKLM:\SYSTEM\ControlSet001\Control\Class\{4D36E967-E325-11CE-BFC1-08002BE10318}' -Name 'LowerFilters' -Value '' -Type MultiString

    If (Get-Service "XenSvc" -ErrorAction 'SilentlyContinue'){(Get-WmiObject -Class Win32_Service -Filter "Name='XenSvc'").Delete()}
    If (Get-Service "XenPVInstall" -ErrorAction 'SilentlyContinue'){(Get-WmiObject -Class Win32_Service -Filter "Name='XenPVInstall'").Delete()}
    Get-WmiObject -Query "SELECT * FROM __Namespace WHERE Name='xenserver'" -Namespace "root\cirix" -ErrorAction SilentlyContinue | Remove-WmiObject
} 
ElseIf (($ComputerManufacturer -eq "Xen") -and (Get-InstalledApplication -Name $appName)) 
{
    Write-Log -Message "$appName is already installed." -WriteHost $True -LogType 'CMTrace'
}
Else
{
    Write-Log -Message "Not a Citrix XenServer virtual machine." -WriteHost $True -LogType 'CMTrace'
}