VS 2010 Express Edition Online registration!

I am new to dotNET, I downloaded Visual Studio 2010 express edition free for 30 days, for practicing. After 30 days it say

you need to register for continue using visual studio c sharp.

After online registration it gave a Key, I entered the key and now Visual Studio continuing.

What is that key for, and how long I use 开发者_如何学编程it? I need to purchase a new one or I continue with this?

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After installing, the programs of Visual Studio 2010 Express will state “For Evaluation Purposes Only”, which run for 30 days. Registration is required to continue using Visual Studio 2010 Express. Registration is free and comes with access to additional benefits. Once activated, the Visual Studio 2010 Express will no longer has the warning message, and lasts forever. Mostly is for evaluation Purpose only.

Express Edition products are basically designed for hobbyists, students, and novice developers...

Link Here (VS 2008 express)

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Visual Studio 2010 Express Edition is free of cost. you no need to purchase anything like. For more details: https://www.dreamspark.com/default.aspx