You cannot upgrade splunk enterprise directly from 4.3.2 to 6.1.x version. You have to upgrade the splunk from 4.3.x to 5.x or 6.0 first, and then upgrade to 6.1.x.
upgrade indexer server from 4.3.2 to 5.x or 6.0
then upgrade forwarders connected to this server to 6.1.x
then upgrade indexer from 5.x or 6.0 to 6.1.x
What Windows OS version you are using ?
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