“One or more ArcGIS ver. 9.3.170 products exist”
Be sure that all other ESRI products are uninstalled before doing this –
1. Browse to your ArcGIS Server 9.3 installation location (should be C:\Program Files\ArcGIS) and delete the entire ArcGIS folder. If you want to use your 9.3 Server configuration files for the 10.1 Server, copy C:\Program files\ArcGIS\Server to a different location.
2. Delete C:\Program files\Common files\ArcGIS
3. Browse to C:\Windows\Assembly and highlight all files that begin with ESRI.ArcGIS…Right-click and choose uninstall.
4. Open up the registry. Browse to HKEY_LOCAL_MACHINE\SOFTWARE\ESRI. Delete the entire ESRI hive.
5. Finally, open IIS Manager and confirm your Server Manager instance from 9.3 was removed from the machine.
6. If you copied the server configuration files, place them back at C:\Program files\ArcGIS\Server.
After these steps, ArcGIS Server 10.1 should install successfully.
Michelle Pearson, Jan 15, 2009
Chris whitmore, Jan 16, 2009