How do I revert my 7105t 4.1 OS Back to the original 4.0

Can you tell me how to do it. Can you just give me a link to it and reinstall it over the 4.1

I am having audio problems, as Tmobile says is common, so they advised me to do this. I did not tell them I have the Hong Kong version. Not sure if it is against their rules. I don't think so. But I want to do it now and call them saying I did it yesterday if it doesn't work. I don't want to ask them how to do it and then have to wait a day or so to see if I still have these audio problems.

Thanks

(p.s. is the bb better than the tmobile sda(forget the name) )

Unistall 4.1 OS from your pc, reinstall your old 4.0 OS you can do it from your CD or look it up in the Blackberry FAQs button above under OS upgrades. Do all of this with desktop manager closed and the BB disconnected from the PC. When you are done reinstalling the old OS (make sure you remove the vendor file) connect your BB to the computer via the USB cable, and restart the desktop manager it should detect that you have a different version and prompt you to downgrade, just follow the prompts along making sure you do a backup. I would unistall any themes that were added including the plazmic theme reader before i start the whole process since these will not work in the older os and may cause you problems.