In vista it's located at C:\Users\username\AppData\Roaming\The Creative Assembly\Empire\scripts
XP C:\Documents and Settings\---NAME---\Application Data\The Creative Assembly\Empire\scripts
You might need to show the hidden files & foldes to find it. So in windows explorer click Tools>Folder Options>View>select show hidden files and folders.
When you make changes, you are advised to make make your own small mod file instead of editing patch3.pack directly. Example You want to edit euro_line_infantry_britain. Instead of editing straight away, go to file>New unit_stats_land_tables Table to create a new table, choose new pack file and this is where you name your mod file.
For range, it's the projectile tab. Change musket_flintlock (range70) for musket_breech loader (range 125).
For reloading skill, change to 100 should do.
I have run into the same problem... I originally said that the pack 2 file being found instead of the pack 3 file was ok, but that was a little premature...I have run into problems as well for that. But I will let you know that I have everything running with the mods that I have made (i.e range/accuracy/armor/ etc..etc...
Now this is what has worked for me so don't flame me if it doesn't work for you.
Above all, make sure you make a copy of the pack 2 and pack 3 file somewhere else and rename it so the editor doesn't edit it (better safe tham sorry, I re-installed this game 6 times before I did this)
1)You need to make a log of what you changed in pack 2 and apply it to pack 3.
1a) After you change what you want to change in pack 2, pull it out of the data folder onto your desktop so the editor reads the pack 3 file and not the pack 2. If you downloaded new content,it will be in the pack 3 file as well as the old content will be in the pack 3 file. Edit the new content that wasn't available in the pack 2 file and save ( remember to have save on the editor) as well as the other files that were availabe in the pack 2 file ( remember the log I talked about?). Don't forget to put the pack 2 file into the data file from your desktop.
2)Until you know what works and what doesn't, don't change any values above what the game has it for (i.e. accuracy is maxed for all at 80 in the editor and reload is at 65) I know m8tal has had more luck with it, but stick with game parameters until you get a hold of it. In other words, check the values by clicking on the top of what you want to change in the column and go with the best. Arty is 450, but 80 (range) is a good value for any infantry and I have had no problems since.
3) Until you get the program running, do not change unit size or horse size.
4) Remember, anything that says Global means that the AI has access to it as well so be careful on what you edit or you will face the same units with the same changes on the battlefield(ouch!!).