A:AnswerThe Hard drive has software on it for Security. Many AV programs flag executable files as malware or viruses. I always suggest formatting the drive prior to use so #1 it's blank, and #2 its formatted to the correct format (NTFS, FAT32, whatever).
A:AnswerSure they can be copied from your satellite box to this drive. Then you can view them separately. Leave out the new DVR and face it == you'll never ever look at them unless you sort out the keepers and delete the rest. No limit to the amount you can record -- get the largest backup drive you can think you'll ever need and it still won;t be enough.
A:AnswerIt depends on the byte size or the amount of the information from each PC. If it will all fit then yes. You could take the drive and split it into two volumes one for each PC. But the easy way have a dedicated drive for each PC, better yet have four drives for each and use one each quarter to do back up.