I have, I kept on getting the convertdata?originalsins0 not found error...  However, I did figure out how to use cmd.exe with convertdata.exe, so I'm that much closer. Another question is that the 'Mods' folder that seem to be standard are in C:/Document and Settings/blah blah blah while the game itself is in my H: drive. Lets say I manage to weed through all the entity files, and make adjustments. How would I innact my mod? Do I just replace the entity files in my game's location? Or do I put it in one of the mod folders?

Okay, where is your mod folder located? This is usually in a different location than where the main game is installed, and you may find it is actually on your C drive. Regardless, the files only reference files in the mod folder, so you shouldn't have to worry about what drive it is in.

To make a mod, just make a new folder in the mod folder. Then make the folders that the files you are modding are contained in. For example if you modded an entity file, you would make a folder within the new folder called GameInfo and put the modded file in there. Enable the mod in game and Sins will load that file instead of the regular file of that name (if it is a completely new file it will load that one in addition to the game files).

If you are having trouble, try downloading and playing a mod to see how it is set up. Or just ask here.

Man, you guys have been super helpful... But there's so much to modding! Ok, so I've been messing around with capital ships, a few things I've noticed is that the game only uses the latest .entity for the item. Considering the Diplomacy has only a few of the older entity files in it, most of the things I mod for Entrenchment would work for Diplomacy, right? So, if I download an Entrenchment mod, Diplomacy will read those files too? Another question is that I finished my alterations to a capital ship, (increasing everything to make it more useful, changed some of the weapons), and placed it in the game info folder of the correspond mod folder like you suggested, but when I load the mod, the game freezes, and I get the minidump error. It also does that when I duplicate points in the mesh file.

I did.

Working for the Kol Battleship, I wanted to add small point defense lasers, so I copied all of weapon-1 (10 weapon points) and added 10 the the NumPoints, (29-39), renaming my copied points weapon-3.

After a little test, I found that they can't have four weapons, so I added weapon-2s to weapon-0, and renamed all weapon-3s to weapon-2s. Adjusted the .entity file so that weapon-0 was the lasertech weapon, weapon-1 was the autocannon, and now weapon-2 was the point defense beam weapon.

Since I have a copy of the entire game elsewhere, I was altering the actual game's files. When I loaded the game, it worked. It showed the new weapon, and the animations were only a little off. 

However, I replaced the modded files with the original again, and put the modded capital.entity and .mesh into a gameinfo folder in the mod folder. Now I get a minidump... If it worked in system, it should work in mod, right?

Edit: I was working with Diplomacy, so I made sure I had an Entrenchment folder, with the .entity inside a GameInfo folder, and outside the Entrenchment, I had a mesh folder, since Entrenchment didn't update most of the meshes, so I'm pretty positive I put them in the right places.

No, I didn't rename any files... What's the entity.manifest?

So, if I add any ships, I have to add the entity to the entity.manifest? Where is the entity.manifest?

any NEW entities NEED to be added to the entity manifest, but if there are no new entity files you can just copy the manifests from the game's expansion folder

all the manifests are in the mod's root folder where you can see the gameinfo and other folders and can put your own notes etc and the game does not read any of the files other than the manifests( at least from my observation)

harpo

I noticed that the capital ships cannot support more than three weapons. Is there any way I can adjust that?

Alright, another modding question (this'll end up being a modding guide, if I slam enough in...). Where the HECK are the graphic files? I see references, HUDICONPLANETMODULE blah blah blah... But where are the icons? I should be super easy to make new icons, but I can find them anywhere.

So I have to go into the Window folder, find the correct file to figure out which image files HUDICONPLANET_PHASEORBITALMISSILEDEFENSE refers to?

They are like the entity files, in the game folder they are bin and will have to be converted to txt like you normally do and then open it with notepad. Remember to place the .brush file in a Window folder in your mod folder and not the GameInfo

Ok, I opened up the HUDIcon-Ship.brushes file, and it shows stuff about pixel boxes, but I don't really know what I'm looking at. There seems to be five different states to each icon, but the pixel box has four numbers, and no reference to a texture file... What am I looking for?