ive also had this problem where i must chagne a list of IPs into there respective ranges
ive always done it by hand, but ive only had to do this liek 2-3 times, im sure a simple bat file might work for this, if no one makes a sweet proggy to do this, i'll give it a try thru a bat file,

edit:
well i got bored and thought i would work on this, after thinking about it for a few seconds, i realized how easy this would be, lol
put this code into notepad
and save it as ip2range.bat
then make an IP.txt that has all the IPs you want coverted to ranges, then run the ip2range.bat file and it will make ranges1.txt with 192.0.0.0 192.0.255.255 format and ranges2.txt with 192.0.0.0-192.0.255.255
enjoy,

edit2: if i think of some more feaures i might develop this a bit more or something