I download amiga forever and amikit.When i install amikit it ask me to put amiga forever or amigaos 3.9.I want to install amiga os like operation sistem windows,so tell me where i can download os 3.9 free and how to install it.Thank you 
AmigaOS 3.9 cannot be downloaded free legally, of course if you hunt the naughty sites you might find it.
To install it, you'd need to run an emulator:
http://www.winuae.net/But you also need the kickstart Amiga ROMs which are also not free.
As advised earlier, the easiest way is just to get hold of Amiga Forever, it's cheap and all set up for you:
http://www.amigaforever.com/If you just want an Amiga-like system, run AROS on your machine:
http://www.icarosdesktop.org/
