I understand that reinstalling Windows on a computer that came preloaded with the operating system can be a bit challenging, Cathi. I'm here to share insights about this. 

When reinstalling Windows on a computer that has the operating system installed, I suggest contacting your manufacturer/vendors. It's important to back up your data before proceeding with the reinstallation. You can save it to a local folder on your computer.  Once Windows is reinstalled, you can then reinstall QuickBooks Desktop and restore your company file from a backup. 

Here's how to create a backup copy of your company file:

1. In your QBDT company, go to the File menu and select Switch to Single-user Mode.
2. After that, go back to the File menu again and hover over Back up Company. Then, select Create Local Backup.
3. In the window, click Local Backup and then Next.
4. From there, select Browse and select a local folder you want to save your backup company file.
5. This runs a test to make sure your backup file is in good shape before you save.
6. Once done, select OK.
7. Click Save it now and Next. You'll get a confirmation message once done.
8. After that, move or copy the backup data to your external drive.

To restore the backup company file, follow the steps below:

1. Go to the File menu and select Open or Restore Company.
2. Click Restore a backup copy and then Next.
3. Select Local Backup and then Next.
4. Browse your computer for your backup company file. It should look like this: [Your company name].qbb.
5. Choose a folder to decide where to save your restored company file. Then select Open.
6. Click Save. 

For complete information, refer to this article: Restore a backup of your company file.

If you need further assistance reinstalling QuickBooks, don't hesitate to mention me in the comment section below. I'll be happy to help you out again. Take care, and have a nice day.