If you have Samsung Kies installed, whenever you plug in USB cable between Samsung Galaxy S II and PC, Samsung Galaxy S2 will be detected as GT-I9100 in Computer. And Samsung Kies will be loaded. You can disable Samsung Kies from loaded automatically by turn off Auto-run ~ Run Samsung Kies automatically when device is connected at Samsung Kies Tools – Preferences. You can read / write your Samsung Galaxy S2 files in this MTP Application mode. However, certain operation like unzip file to SGS2 directly is not possible in this mode.
USB mass storage