I tried to udpate rails from windows using instant Rails, using the follwing statement:
gem update --system
but an error appears and I don't know what's the problem. Is there other ways to update it or solving the probelm?
First, I wouldn't recommend using InstantRails for any type of Ruby programming on Windows. There are far better ways to install Ruby and the necessary components on Windows.
Second, we could help troubleshoot better if we knew what the error said. However, I HIGHLY suggest installing Ruby and Rails as described in the links above.