Final answer:
Kathleen should examine the %SystemRoot%\MEMORY.DMP file to find data contained in the memory of an offline Windows system since this file has the contents of the system's RAM at the time of a crash.
Step-by-step explanation:
Kathleen is looking to recover data contained in the memory of an offline Windows system and the best place for her to look is %SystemRoot%\MEMORY.DMP. This file is a memory dump file that Windows creates when the system crashes, also known as a Blue Screen of Death (BSOD) event. It contains the contents of the system's volatile memory (RAM), which can provide useful information for troubleshooting but can also hold data that was present in memory at the time of the crash.
The Registry could also be of use as it contains configurations and settings for software and hardware on the system, but it would not contain the actual data of files or programs that were open when the system went offline. A system restore point file contains system settings and configurations at a particular point in time and not the contents of live memory. Therefore, Kathleen's best chance to find the data she needs would be to analyze the MEMORY.DMP file if available.