If both are V6 boxes:
These will update via the network with the Horizon firmware. As the disk is reformatted you will lose any recordings. Both boxes will still record, but you will have to specify which box you want to record on for each recording. The recording list is pooled, so you will see all your recordings as standard in the list. When one of your boxes fails you will get a mini box as a replacement, which will halve your recording capacity.
If you have a TiVO 500 as a second box.
This will be replaced with a mini box, which as described above has no recording capacity.
