How to start working on SharePoint 2010? And what are the pre-requisites?

I have experience in .net but never worked on sharepoint development. I shall like to know how I can start working on Sharepoint? I know, I can develop some web-parts for it. But I am not sure what environment I shal开发者_开发问答l need to start.

Do I need to install Share point portal server on my machine to work on it?

If it is mandatory, is there a developer/express version?

The work is purely from the angle of development on SharePoint. Please guide me.

Important update:

Now that I have an access to a sharepoint server (a site on a sharepoint 2010 server) where I can do changes to. Provided I have created some XAP (silverlight part), how to deploy to this server? Can I use the upload web part link to upload the XAP? If I upload, where will it reside?

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One point -

For SharePoint 2007, you will have to install SharePoint on the same PC as your development box. That means your dev PC must have either Windows Server 2003 or 2008 installed. You cannot write code in Visual Studio and step through it if the SharePoint site is located on another computer.

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The best as i think to to install Virtual machine take the VHD file from any one who has sharePoint install in it. Just use that VHD file , you get the complete environment includes your all basic functionality.