It should be the same as on any other Windows System, though if you are not the main administrator it could get more complicated. Have you enabled cheats and they are not working or do you not even know where to start?
Okay, first make sure that the file isn't set to read only. If not, then I would give all users on your computer full control over the file in the security settings. I Vista I had this problem where I was the Administrator yet for security purposes it put me under the "Users" category. I never got the point of this because as an Administrator I could just change the permissions, but regardless you might have a similar problem.
I know how to solve your problem in 7, however the cheats don't seem to work for me anyway. Open notepad, copy all the info in swkotor2.ini into the new file, add the enablecheats=1, name it swkotor2.ini and save it to your desktop. Delete the original ini in the folder, drag the new one to the folder and voila.
Granted, I can't seem to make any cheats work in the first place, but it does bypas the issue.