How would I go about doing this?
I've checked -- How do I downgrade the OS on my BlackBerry? - BlackBerryFAQ -- but it makes no sense to me. When I choose my carrier, all it does is take me to the tmobile website where I can upgrade desktop manager.
To downgrade your OS you have to go to your carrier site and download the Device software (for Tmo i think its under BlackBerry Downloads) and it will ask you to list your current device. After that it will give you the link to the latest release they have put out. Is there a particular reason you wish to downgrade?
But I want to downgrade because i couldn't download my instant messenger on 4.5os (it didn't recognize my phone as a 8100pearl), it took up a lot of space, and i wanted to be able to use colorpearl.