Reformatting a computer hard drive without restore disks is possible, but it requires caution as all data will be lost. Users can access the DOS option by restarting the computer and using specific key combinations to enter setup mode. From there, the command "format C" can be executed, and the Windows installation disk can be accessed through the CD drive, typically designated as D: or E:. If the hard drive is partitioned, files can be moved to another drive before formatting the primary drive. It's important to have the necessary installation disks for the operating system, especially if upgrading from an older version, as both original and updated disks may be required. Some users have experienced issues with resolution and driver compatibility after using restore disks, necessitating additional installations and configurations. If errors occur during installation, checking disk space and ensuring the correct drive is being referenced is crucial. For beginners, detailed instructions on accessing setup modes and executing commands are recommended, along with the suggestion to avoid unnecessary backups that consume disk space.