Please take note you need to free up your internal memory before proceeding, at least have more than 4MB free and very important to have two SIM card in the phone while installing it and setting it up so you dont have setting up favorites failed
1. Download the Raw file from here
note the file is a zipped file.
2. unzip the downloaded zipped file, then copy the whole folder to your memory card (advisable to do this step on a computer).
3. Now goto the folder, DO NOT launch the whatsapp application inside the folder just yet.
4. Copy the application from the memory card to your My Apps or Games.
5. Now go back to the initial folder and delete it.
6. Now go to the whatsapp application in your phone, click the option button and click update version, let it update then you can open the application...follow all instructions and be patient, when it is finally opening, you will get updating notification enabler
let it load, it will fail and tell you phone not supported, close it and your whatsapp is installed and working.
Update: for those asking how to get the unzipped version download this two files here and here , copy them to a folder on your memory card, then rename them like this WhatsApp_jar will now be WhatsApp.jar then WhatsApp_jad will be WhatsApp.jar after this follow the steps from 4. above.