What specifically was damaged?
Certain extensions can only have one version installed. For example, 8.0 comes with FieldPoint 5.0, which is not supported in 6.1 - if you install FP 5 you lose all of your FP support in 6.1. If you don't install FP 5 you don't have support for newer products like the 180x and you would probably have to manually copy the VIs from the older version into the 8.0 directory.
The only way around this is probably to keep a machine for older versions or maybe try some of those virtual computing programs which allow you to easily switch between your various "PCs".
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