Hello!
1. Why should an investigator not unplug a computer that may contain chat or instant message conversations?
Unplugging the computer will cause the data located in RAM to be lost, and RAm is where most chat and instant messaging conversations are likely to be stored.
2. Why are online conversations conducted using chat and instant messaging more difficult to recover than email messages? Where are files containing such conversations likely to be stored?
These types of conversations are more difficult to recover because most of them are not saved by the parties involved. Files containing chat and instant messaging conversations are most likely to be stored in RAM.