If you download a version for your phone like 8320 why do you have to delete the vendor file?? I never have

Yes, if it is from a vendor other than the one branded to your device. As for a beta OS, absolutely.

Why would you want not to do so?

I dont know why I would not want to do so....because I never have..and cant tell the diff!!! Because i am having the same exact problem as everyone else with the vendor file the same.

Actually, many of the beta versions have "empty" vendor.xml files. So, sometimes it's not required. There is no difference as to what's loaded to the device, though. Vendor.xml is like a yes/no. The OS will either load or it won't.

It is required anytime you load an OS released by a carrier other than that on the BB. You will be able to tell a difference if you don't , in that it will not load.

Some of the Beta OSs are different, correct.

Feel free not to delete VENDOR.XML.
If you start Desktop Manager and the new version doesn't load, then delete it.

Feel free to ignore any advise here.

Ok thanks!!! I hit up the search button just could not find reason...Now I understand!!!

Certainly, feel something, at least.