Yes. See this document, and be sure to select the your Splunk version in the upper right.
Generally speaking, to exclude splunkd.exe you add a custom stanza at the global level and include a regular expression EXCEPT for splunkd.exe for the proc attribute. The way the proc filter works to send everything that matches through, and it drops everything that does not match.
I've gone through a few, but here's the latest one I got from someone at Splunk:
proc = (.(?!\splunkd.exe).)
There are stars after the dots, but they aren't showing up in the comment.
this assumes you are using a version of splunk older than 6.0. if you're using 6.0, the same procedure applies, but all the changes should be made in a local copy of inputs.conf