As @venkatasri already pointed out - you can't just conjure data out of thin air - if the original event doesn't include the information (and typically it doesn't - why should it? You don't need the extra amount of wasted storage only to have the information which you typically should have otherwise).
And your windows admin will most probably _not_ be able to force windows to include such info in the logs (again - why should windows send that in the event?).
Typically, in all kinds of monitoring software you usually have some form of an asset database separate from the events themselves and a method of correlating the source identified from the event with the data in said database. In case of plain Splunk Enterprise you can gather such info in a lookup table and dynamically enrich your data on search. If you have Enterprise Security, there are additional options of having such asset db created (semi-)automatically for you.
