Unable to upgrade to XenServer Tools 7.0 - Error : Windows Management Agent Failed to Install

After upgrading to XenServer 7.0 - Unable to install Xentools on Windows VMs.

Windows Management agent Failed to install.

1) Download the psexect tools from https://technet.microsoft.com/en-in/sysinternals/bb897553.aspx 

2) Open Command prompt navigate to the path where psexec downloaded

3) Run regedit.exe from command line using psexec

psexec -i -d -s c:\windows\regedit.exe

4) Delete the following registry entries:

• HKLM\SYSTEM\CurrentControlSet\Enum\XENBUS
• HKLM\SYSTEM\CurrentControlSet\Enum\XENVIF

5) Reboot the machine.

6) Install the management tools for x64.

7) Reboot the machine.

Note :  psexec gives the full access to the registry as SYSTEM user (highest privilege user) and should only be used to delete XENBUS and XENVIF entry under ENUM (if present).

We could see that in C:\programdata\programdata\InstallAgent\1.0.5961.21197\InstallAgent.log, it was failing to fetch information related to XenBus and failing.

dvi: Default installer: Exit dvi: {DIF_INSTALLINTERFACES - exit(0x00000000)} 14:06:24.466 dvi: {DIF_INSTALLDEVICE} 14:06:24.466 dvi: No class installer for 'XenServer PV Bus' dvi: CoInstaller 1: Enter 14:06:24.466 ! ven: XENBUS_COINST|Entry: 8.1.0.63 (22/1/2016) ===> ! ven: XENBUS_COINST|Entry: INSTALLDEVICE PreProcessing ! ven: XENBUS_COINST|DifInstall: Flags = 01800028 ! ven: XENBUS_COINST|DifInstallPreProcess: ====> ! ven: XENBUS_COINST|AllowInstall: ====> ! ven: XENBUS_COINST|AllowUpdate: ====> (XEN) ! ven: XENBUS_COINST|AllowUpdate: (XENBUS) ! ven: XENBUS_COINST|AllowUpdate: (XENFILT) ! ven: XENBUS_COINST|AllowUpdate: ! ven: XENBUS_COINST|GetDeviceKeyName: none found ! ven: XENBUS_COINST|GetDeviceKeyName: VEN_5853&DEV_0002&SUBSYS_00025853&REV_02 ! ven: XENBUS_COINST|GetDriverKeyName: {4d36e97d-e325-11ce-bfc1-08002be10318}\0024 ! ven: XENBUS_COINST|MatchExistingDriver: ! ven: XENBUS_COINST|GetDriverKeyName: {4d36e97d-e325-11ce-bfc1-08002be10318}\0025 ! ven: XENBUS_COINST|GetMatchingDeviceID: XENBUS\VEN_XS0002&DEV_IFACE&REV_00000001 ! ven: XENBUS_COINST|SupportDeviceID: fail2 ! ven: XENBUS_COINST|SupportDeviceID: fail1 (Íå óäàåòñÿ íàéòè óêàçàííûé ôàéë.) ! ven: XENBUS_COINST|SupportChildDrivers: fail9 ! ven: XENBUS_COINST|SupportChildDrivers: fail8 ! ven: XENBUS_COINST|SupportChildDrivers: fail7 ! ven: XENBUS_COINST|SupportChildDrivers: fail6 ! ven: XENBUS_COINST|SupportChildDrivers: fail5 ! ven: XENBUS_COINST|SupportChildDrivers: fail4 ! ven: XENBUS_COINST|SupportChildDrivers: fail3 ! ven: XENBUS_COINST|SupportChildDrivers: fail2 ! ven: XENBUS_COINST|SupportChildDrivers: fail1 (Íå óäàåòñÿ íàéòè óêàçàííûé ôàéë.) ! ven: XENBUS_COINST|DifInstallPreProcess: fail4 ! ven: XENBUS_COINST|DifInstallPreProcess: fail3 ! ven: XENBUS_COINST|DifInstallPreProcess: fail2 ! ven: XENBUS_COINST|DifInstallPreProcess: fail1 (Íå óäàåòñÿ íàéòè óêàçàííûé ôàéë.) ! ven: XENBUS_COINST|Entry: 8.1.0.63 (22/1/2016)

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.