Win7 are usually set to English. How about for those people who don't speak English and wanted to use the computer using their own language? Vistalizator comes in to help. Without reformatting the computer to initially set the language, you can install this multilanguage pack and set to whatever language you require it to.
Here are the steps:
1. Go to this site and install Vistalizator. Go back to site then look for available language packs, like Arabic, Spanish, Chinese, etc., then download your language packs. Save in your desktop for easier storage. MUI stands for Multilanguage User Interface. Your download usually has MUI on it.

2. Double-click on the downloaded file so Vistalizator window will open. Click on Add Languages, and select the file that you saved in your desktop, and finally click Open.

3. Click "Install Language" and wait until this finishes the installation.
4. Confirm window will come out saying "Done! Do you want to make Arabic language the new display language?". Select Yes.
5. Press OK. And you'll notice that there are 2 languages installed on the Vistalizator window (2nd image from this blog) English and Arabic. Click Exit and the computer reboots.
In case you encounter error during the installation, pls refer to this guide.