keep this in mind.... that the ppl that r supossed to b trained still tellin u to do a few things wrong....
And now here are answers to your original questions:
Multiple AV programs can be installed in a single machine, if only one real-time protection is turned on at one time. But normally we don't recommend this for normal users as this could get complicating.
Uninstallers are supposed to remove their entries installed in the registry. It is only in instances that the uninstallers are not coded well that registry traces are still left in the registry, and in this case a registry cleaner can be used. Yet keep in mind that registry cleaners are not fool-proof and a registry backup is recommended every time you use it.
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