|The computer is worth more is it has an operating system and some office software.|
If you never made any recovery disks you MAY still be able to do that. If you make recovery disks test them for validity. If good, then wipe the entire disk and then restore using the recovery disks.
The recovery set is designed to install everything. Even OEM makers realize hard drives die and a method to reinstall everything is required. That is what the recovery set should do.
If you are concerned that won't work then image the disk to a second hard drive or optical disk. That will give you an insurance policy and also will give you a backup of the files you will inevitably forget to backup before wiping the drive.