First of all:
uninstal android SDK , then check the box to delete any trace folder related to Android and manually delete it from the Program Files folder and from the Documents and Settings folder,
then uninstall java JDK and eclipse ,
(which means that you clean your computer of any thing related to Android development development) ,
now start again as shown below:
1- Download the latest java from this link: http://jdk7.java.net/download.html then install it.
2- download the latest version of the Android SDK from this link: http://developer.android.com/sdk/index.html then install it, after installation is complete do not run it .
3- download the latest eclipse from this link: http://www.eclipse.org/downloads/packages/eclipse-ide-java-ee-developers/junor copy the zip file to the C folder and extract it to the C folder itself,
RUL ECLIPSE THEN:
1-Download the ADT plugin:
a) Launch Eclipse, then choose Help> Install New Software.
b) Click "Add" in the upper right corner:
In the Add Repository dialog box that appears, enter this
for plugin Name: ADT,
and the following URL for the location: http://dl-ssl.google.com/android/eclipse/
Then click OK.
d) In the software dialog box, check the box next to the developer tools and clicks.
e) in the next window you will see a list of tools to download,
Click on.
f) Read and accept the license agreements, click Finish.
H) When installation is complete, restart Eclipse.
2- Select Window> Preferences ... to open the Preferences panel
a) Select Android from the left pane.
b) The location of the SDK in the main panel, click the browse button ... and find the downloaded SDK directory, then click "Apply", then "OK".
3-open in eclipse: window, then Android SDK manger and download any platform you want to start development from.
several times, possibly due to the loaded android site server, it gave an error, and then later it will select the entire package you downloaded that you previously determined and download it successfully.
hope this help.