I am working over linux in our office for development over Ruby on Rails but in home i have Windows XP installed. It has different IDE installed for .NET and PHP development. So i don't want to get rid of those stuff also so kindly guide best IDE for Ruby on Rails Develpment over windows with MySQL as Database..
I'm also currently working on Linux and NetBeans. Netbeans also supports Windows and you can have PHP as well. But unfortunately NetBeans has discontinued their Rails support from version 7.0. So long term, it might be a problem.
Another one is RedCar (http://redcareditor.com/), this is also good.
Also Aptana RadRails (http://www.aptana.com/products/radrails) can also be used (they offer Eclipse plugin also).
And if you are looking for a paid one I would say go for Rubymine (http://www.jetbrains.com/ruby/).
But as the final note. I have setup dual boot in my home laptop and do all the development except (.net) in Linux because you know Linux rocks :D