You have to change the index at the level of the script that collects WMI:
in inputs.conf:
[script://$SPLUNK_HOME\bin\scripts\splunk-wmi.path]
index = os
Looks like in version 5+ you can set the index in wmi.conf file.
You have to change the index at the level of the script that collects WMI:
in inputs.conf:
[script://$SPLUNK_HOME\bin\scripts\splunk-wmi.path]
index = os