Can you give a bit more detail? Have you ever been able to successfully run 'rails server' on this windows computer? Was it working before adding the last gem?
FYI, very few of us develop in a Windows environment and will not be familiar with Windows specific errors. If you are serious about Rails development, strongly consider Linux, I like Ubuntu, or using a Mac.
I looked the error and noticed that your version of ruby is 2.2.0. I had this problem and find that nokoguri isn’t compatible with 2.2.0. The version 2.0 of ruby is more bugless. Install the version 2.0 of ruby and be happy. 
And paste a text log, not a screenshot!
nothing except a screenshot.
Which version of rails are you using? (rails -v) Have you run bundle install
And as others have said copy/paste stuff here, do not use screenshot please.
Colin