I had to back up one of my VPC's to DVD - a just in case measure as I head down to Florida or DevConnections with a VPC dependent demo. In my folder was the VPC drive file and an extra file, I thought a backup. The main file was about 4GB and the second about 3GB. So I backed up the main file and the vpc settings file and then went to test the backup which gave me hard drive errors - I couldn't boot up. Out ofcuriousity, I made a copy of the VPC file on my hard drive.Same problem. Then I dropped that "backup" (V01 extension) file in there and it worked.

A little googling tought me that the drive capacity for a VPC is 4 GB nnd my 7GB file was split into two drives. Aha! Here is a good explanation from JoeN at Microsoft who had learned the hard way, too.

So, I had already made he back up of the first part of the VPC at 7:12 pm. Now the timestamp of the two files that are in use are past that. Whichmight have meant having to reburn both files so that I had a matching pair. I did a little experimenting with mismatched files (that had no changes, just had been opened up) and the VPC disk went through a big repair but then booted up  just fine. I still may just toss that frst DVD and have a matched backup. Just in case.