Choose the correct preposition

1. This laptop isn't
   [with|in] stock.
2. It's very expensive to get a laptop repaired if it's not
   [with|under] guarantee.
3. The shop assistant exchanged my broken printer
   [for|from] a new one.
4. The PC was delivered free
   [of|on] charge.
5. I don't know what's wrong
   [at|with] my PC.