Final answer:
The technician should run CHKDSK to determine the problem of corrupted files.
Step-by-step explanation:
To determine the problem of corrupted files, the technician should run CHKDSK. CHKDSK (Check Disk) is a Windows utility that checks the integrity of a disk and fixes any errors it finds. By running CHKDSK, the technician can identify and resolve any file system issues that may be causing the corruption.
Performing a backup of all drives, while important for data safety, may not directly help determine the cause of corrupted files. Ensuring all Windows updates are installed is a good practice for system stability but may not specifically address the corruption issue. Running defragmentation is useful for optimizing disk performance but does not directly deal with corrupted files.