How can I select the games from a backup drive to restore on Steam?

I have a USB drive with CSGO, Portal, Portal 2, half life 2 on it, and I own all the games. I put in the drive and do the usual, but it's asking fora CD key. That's because there's a game in there that I don't own, but I own all the others. What can I do?

Solution 1:

• Open Google and type App ID "game name". This will be the game you do not own (e.g. Dota 2 would be "570").
• Go to the backup directory and open "sku.sis" in Notepad.
• Scroll sideways until you reach the section where it says "Apps".
• Look inside the brackets for the App ID in question. The first number will indicate the listing number off the backup and the 2nd the App ID. (e.g. "0" or "570").
• Delete the index number and App ID of the game in question (e.g. "0" or "570").
• Save and close Notepad and try restore from backup again.