Explanation The main purpose of creating and storing an external disk hash value when performing forensic data acquisition from a hard disk is to validate the integrity of the data during the analysis. This is done by comparing the original hash value of the disk to the hash value created during the acquisition process, which can be used to ensure that the data has not been tampered with or corrupted in any way. Additionally, by creating a hash value of the disk, it can be used to quickly verify the integrity of any data that is accessed from the disk in the future.