Cumulus Support

I have Honeywell TE923W, Oregon WMR200, LaCrosse WS-2812U-IT, and Ambient Weather WS-2090. Each feeds its data via its own software (Weather Capture, Virtual Weather, Heavy Weather, and Easy Weather respectively). I copy these data from the individual software to Excel 2003 on a Windows 7 computer.

Will installing and using Cumulus interfere with this?

It depends on what you intend to do with Cumulus. You can't run it at the same time (i.e. simultaneously rather than alternately) as other software with the same weather station. And logger download from a WMR200 is 'destructive', i.e. once it has been downloaded, it's gone.

I want to use Cumulus only to retrieve data from the Ambient Weather WS-2090 in a format that I can copy to Excel. I don't want Cumulus to communicate/interfere with the other stations at this point.

Yes, that will be fine. Cumulus doesn't know how to talk to your Honeywell and LaCrosse stations, and won't try to talk to the WMR200 if you configure it for the WS2090 when you first run it.