Paul,
To go from 2.1 to 2.5 you have to use the prepare.exe file that will convert your 2.1 files to 2.5 files. 2.5 stores the files in a different place under your My Documents / Vixen compared to 2.1 that stores the in the same folder.
I use 2.5 for the last 2 years and prefer it to 2.1. I have found that I have to use a couple different versions for the best set up. (IE 2.5.0.8 has been great for the schedule, but 2.5.0.3 is better for doing the actual sequence programming/preview review).
You can get the prepare here: You are not allowed to view links.
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LoginHope that helps,
JS
PS: I highly suggest as with anything you back up your 2.1 Vixen folder onto another computer or thumb drive in case you choose to go back to 2.1.