MS-DOS and Windows 2000

I had my computer changed from Windows ME, after being eat up with spyware, to Windows 2000. It’s been a few months now and when I try to download anything I get an error message that MS-DOS and
Windows are not suitable for running together. What can I do if anything to get this problem straightened out? The person I had “supposedly redo” my computer is no longer around my area so I cannot take it back to them. Can you tell me anything that would help me??