I want to go live with my silverlight 4 application and host it on the web but some of the web servers i looked at ask if i want the web server to be iis6 or iis7 but im using windows xp and that uses iis5.1 so im a little lost on how to do this. Also any suggestions on where to host silverlight applications
To host Silverlight, you don't need any specific type or version of a web server. Whatever they have will be ok.
If you have any server code (asp.net?) then you want to make sure it is IIS, but even then, version 6 or 7 will still work.
Well for simple hosting of a silverlight application you would not have to be concerned about the hosting server, it could even be Apache.
However, if you have server side code which your SL application needs to communicate with, like a WCF or ASMX web service for example, then you would need to consider the hosting envrionment and the installed framework version etc.
Your choice between IIS6 and IIS7 depends on your requirements, if you do not require a specific version the go with what you can get. Personally I prefer IIS 7 so I would focus on that.