Item Upgrade mod is packed as a self-decompressing .rar archive, and changing the directory should work on your computer - it certainly works on mine. I suggest that the problem is on your end.
Well, generally the advice would be: look at the code in item upgrade pack and start from there. If you understand .d , .baf and .tp2 code and know how to make items, then, basically, you are all set, and it is trial and error from there. If you want to know how to add dialogue/interject into dialogue/create items/wrap up your mod, some of the tutorials in the tutorial section will probably help you. If you have more specific questions than this, like "I have a parse error on line 74, here is the code. Can anyone point out the error to me?", people will generally answer and try to help.
I mean I want to add to the item upgrade pack. I want to make items for cromwell that he can make out of other items. The tutorial section moved it to Infinity Engine Q&A, but no one answered there.