That script will not work for you if the IP is non-resolvable (like mine). Instead I recommend you use the whois servers (ARIN, RIPE, etc).
I coded something that finds the appropiate whois server and returns some of the info from it in a @Window automatically with a single command (/ipwhois <ip>). I jsut uploaded it
here (just make sure you unzip the country-codes.txt file to your mirc main directory).
Note that for some big international ISPs (like AOL) the country you always get is the US, even if the user is in another country.
Also, the format of the text that the whois servers return changes from time to time. The last time I used that script was over a year ago. I doubt it, but it might not work correctly for some IPs anymore.