Installation of android SDK.

Now it is very easy to install android sdk in your windows.But in older process you have to do lot things like you have download eclipse, Android sdk and then you have setup the ADT plugin. 
Now Android provides you all in-built SDK and make it easy in 2 steps.
Step 1: Download and install java.
Step 2: Download eclipse that having in-built android sdk.

Now you can develop the android apps.........

How to download and install java?

For developing an android app you should have min 1.5 java version. If you don't have download it here.
1. Double click on a downloaded file and install java in the default directory path, C:\Program Files\Java
2. After the installer finish, read and accept the license agreement. For mostly, the typical install will be fine.

3. Then click finish. That is it, your installation complete.

4. And then set the CLASS-PATH and PATH. Copy the java installed directory paths like  "C:\Program Files\Java\jdk1.7.0_05\bin" for System Variable ,

 "C:\Program Files\Java\jdk1.7.0_05\lib" for User variable and follow the below process.

Windows XP

1. Select Start, select Control Panel. double click System, and select the Advanced tab.
2. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
3. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
4. Again click Environment Variables. In the section User Variable, click on new and give the following values.
   Variable name = CLASS and variable value ="the whole path" you copied from lib folder.
5. Click OK.
   
    

Windows Vista:

1. From the desktop, right click the My Computer icon.
2. Choose Properties from the context menu.
3. Click the Advanced tab (Advanced system settings link in Vista).
4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
5. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
6. Again click Environment Variables. In the section User Variable, click on new and give the following values.
   Variable name = CLASS and variable value ="the whole path" you copied from lib folder.
7. Click OK.

Windows 7:

1. From the desktop, right click the Computer icon.
2. Choose Properties from the context menu.
3. Click the Advanced system settings link.
4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
5. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
6. Again click Environment Variables. In the section User Variable, click on new and give the following values.
   Variable name = CLASS and variable value ="the whole path" you copied from lib folder.
7. Click OK.

Windows 8:

1. Drag the Mouse pointer to the Right bottom corner of the screen
2. Click on the Search icon and type: Control Panel
3. Click on -> Control Panel -> System -> Advanced
4. Click on Environment Variables, under System Variables, find PATH, and click on it.
5. In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
6. Close the window.
7. Reopen Command prompt window, and run your java code.

Thus the complete java installation process.

How to download Android SDK?

Now you no need to download eclipse. You can download Eclipse that built android sdk.
Download link here.
Click on "ADT Bundle for windows", accept the agreement and mark the option that your system supports either 32 or 64-bit. Download and extract it.
Open the Eclipse file and enjoy the coding..................