Editing Dat files (May Have been asked My apologies)

I couldn't seem to find info on this through searching, All I want is to know How to go about editing my own iteamtype.dat files I am just not 100% satisfied with the ones I found so I figured I should make my own that i'll share on here but i'm unsure where to start.

Well most itemtype.dat files are encrypted, therefore uneditable. If however you find one that isn't open it up with notepad and screw around with it.

1st, you need a proggy that can decrypt and encrypt dat files (search for itemtype AND decrypt). After decrypting, you can edit the file with any text editor. Encrypt your file again when your done et voila, you made your own itemtype.dat

Thanks Jalan, I'll try searching that. I knew i needed to decyrt is somehow just didn't know what i might need to use for it.