NT Workstation changed to shared itself

I’m sorry if this isn’t the right place to ask this question, but looking over the choices was not sure where to list it. I’m running NT4 with SP6. For some reason, it automatically keeps switching over to to share C, WINNT, and F which is the onlyother partition. At one time I installed software to access other computers over the internet. Is this, or something like it messing with my setting? Or is there possibly something more sinister going on here (virus)? I’m about ready to reformatanyway, but would like to know how to fix the problem if it pops up at a later date
Thanks
Roland