why ArcGIS for Server Setup cannot run while a newer version of ArcGIS for Desktop present?

[yinkitw]

I have no idea what is going on, ArcGIS for Desktop 10.5 works fine to me and I just want to temporary install older version of ArcGIS for Server to see If it could get rid of a problem I encounter earlier with ArcGIS for Server 10.5

[JayantaPoddar · Accepted solution]

You can not install ArcGIS components of multiple versions in the same machine (except web adaptor). You need to either

1. Upgrade ArcGIS Server to 10.5. or

2. Downgrade/uninstall ArcGIS Desktop to 10.4.1. or

3. Use separate machine to install ArcGIS Server.

[yinkitw]

Got it, looks like 3. would fit my situation. I hope there are spare machine for me to do so.