Hi osamashafiq, and welcome to AF
As that's an Orange UK Desire I'm afraid we won't be able to find the original firmware. No Orange UK Froyo RUU was ever released or leaked. But you do have some options - won't be able to put links in at the moment, sorry.
One option would be a "rooted stock rom". These are very much like the original firmware, just rooted. The All Things Root Guide sticky post in this forum has a link to an index of desire roms, and you can find a few in there.
If you want to unroot and return to official firmware, the official Android 2.3 upgrade from HTC will run on an Orange handset. You can find this at shipped-ROMs.com, under Android, device name bravo (not desire!), near the bottom of the page. Unzip it and there is a .exe file which is the ruu. Boot phone into fastboot mode (boot while pressing the back key), connect to pc and run the ruu. This will wipe the phone and remove the custom recovery as well as loading an unrooted HTC ROM.
I think there is one Orange UK RUU there, but it is really old and you'd need to use some tricks to make it run (as the hboot you have is newer). I could not recommend it.
The final option is to make a Goldcard, as described in the rooting faq (also linked in the sticky post), and then flash a non-orange RUU. I don't know whether any others (such as Asian region) would have better Urdu support than the stock 2.3 RUU - I know nothing about that I'm afraid.
Original firmware for Orange UK Desire
