If you're using the LabVIEW 2012 SP1 Touch Panel Module or older, NITPCService.cab can be found in the directory listed in the document I've linked below.
How Do I Configure the NI TPC Service on My Touch Panel Device?
http://digital.ni.com/public.nsf/allkb/DE177828D27A14A48625734E00768B66?OpenDocument
However, the process for installing the touch panel service changed with the 2013 touch panel module. The process for installing the touch panel service on devices supported by the 2013 Touch Panel Module is detailed in the document "Getting Started with the LabVIEW Touch Panel Module" (which I've linked below) on page 2 in the section "Installing Support for NI TPC Service." This installation procedure differs from the older installation process referenced above. This updated installation no longer makes use of the NITPCService.cab file; see the document below for more details.
Getting Started with the LabVIEW Touch Panel Module
http://www.ni.com/pdf/manuals/371940g.pdf
Regards,
Ryan K.
Product Manager, ATCA and BEEcube
National Instruments
