To activate unicode fonts on your operating system
Go to Control Panel>Regional Setting>Languages>(Tick)Install files for complex script........
Note: You can leave blank "Install files for east asian Languages"
A pop-up window will appear 'select OK'
Then Insert windows XP cd Into CD/DVD Drive
And specify path for required files
Reebot and you Have Done!
If Still having problem then download
ARIALUNI.TTFTry to Decode Mangal font with this One.
Enjoy!!!!!!!