Following the Driver Installation Notes For Windows 2000:
1. Uninstall previously installed drivers. From the "Device Manager" right-click on the Digi adapter(s) you would like to uninstall from the system and select "Uninstall". 
2. Run the program DgClean.cmd to remove existing INF files for your adapter. This will ensure the new drivers will be installed correctly. Dgclean.cmd is located in the folder with your downloaded drivers.

Running the DgClean.cmd results in an error "Access Denied."

Cause:

By default the WINNT/INF directory is hidden so DGClean.cmd will not be able to find the necessary files in the WINNT\INF directory
to delete them.

Solution:

1. Make sure you are logged in as Administrator.
2. Double-click My Computer, and then double-click the hard drive on which you installed the Recovery Console.
3. On the Tools menu, click Folder Options.
4. Click the View tab.
5. Click Show hidden files and folders, clear the Hide protected operating system files check box, and then click OK.
6. Now try running DGClean.cmd.  
7. If it fails, you can go into the WINNT\INF directory and manually delete the OEM#.INF files that pertain to Digi.
8. Now reboot your computer and the new driver should be loaded.