According to the official site, scapy is designed with linux in mind. Everything you should need is here. But, it looks like some of the utilities that scapy depends on do not support anything older than 2.5.
Can you use py2exe to bundle a different python interpreter with your app? Since you have to stick the app on the machine anyway, why not just give them a single "executable" with a different version of python compiled in.
You could use NSIS to install the thing, along with the appropriate dependencies. I.E. libpcap and friends for your version of python and scapy.