Cutting video corupted part

Hello,

I have a video file (rmvb) in the middle of this file there are few minutes corupt and I want to cut this corupted part and throw it away without lose the quality and reconvert it. What sofware do I need?

And another one if I split a video file in 3 part and than I want to join it just with 2 parts to become 1 file, what software do I need?

Thank You.