I have been using Amplitube 3 quite a bit and like it. There are a lot of different amp simulators for computers out there so a lot of different opinions. You can download Amplitube 3 for free, you will only have access to a few amps and effects, but you can try it and see if you like it. There are also free amp simulators with a few amps. I am mostly using Amplitube.

You might need some software to record the audio too. I guess Amplitube can do some simple recordings and you can use Audacity which is free.