If you want to use multipe (older) versions off Citrix XenCenter on one Windows server, you have to install the application in this order:
start with the oldest version - e.g. 6.50
use the default directory (c:\Program Files (x86)\Citrix\XenCenter)
if the installation ends without errors, rename the directory to the version number (e.g. XenCenter650)
start with the nex version - e.g. 7.12
use the default directory again
rename this dir to XenCenter712 again
install e.g. 8.20
and rename this also …
Now you have three working version.
This is needed, because the old XenServer 6.50 server and pools can't managed by the new versions of XenCenter.
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