saving CS6 files MAC/IBM

I just had to replace and reconstruct my computer. the first file I save after opening CS6 wants to default to MAC format. IDK that it makes a difference anymore but I cant find anywhere in the prefs to set the default to IBM

I don't know if this works because I have never tried to do it myself but I understand that the Preferences file can be deleted and changed by starting the program while holding down Ctrl/Alt/Shft.