Ok so I had an idol half hour earlier today. I had a look in the 'Big FAQ' and found the themes.zip to load additional themes on your Blackberry.

I'm in the UK and have a 7290 badged up as T-Mobile.

Trouble is, I tried the themes, didn't really like them and thus removed them using application loader. Problem is it seems to have overwritten the default theme on my unit, when I removed them, it went to a black and white, incredibly basic (and completely awful) theme. The nearest I can get to the original (which was the default 7290 small icons I think) is by loading the themes back on, selecting the small icons 7290 theme, but it doesn't display properly, the fonts for the network provider, GPRS single indicator etc are wrong...but the icons are correct.

If I take the battery out and leave it for 24 hours will it loose these new themes and revert to the out-of-the-box theme?

Nope. You are going to have to use Javaloader to erase the BB, and then reinstall the handheld OS (WITHOUT THE ADDITIONAL THEMES).

..oof is that as hard as it sounds? Any pointers on exactly how I can accomplish this (and claw back my 'dont mess' dignity) would be greatly appreciated!

There is a really good thread on reloading the handheld OS. Search for the phrase "javaloader" and someone has (somewhat) automated the tasks.

Before you get started, make sure you do a backup, if you can.
Download the latest handheld OS from your carrier and execute it.
Follow the instructions for Javaloader
Restart Desktop manager and it should reload the OS
Restore from the backup if necessary.

..I toyed with something similar today, my handheld has os 3.8, I downloaded the latest desktop manager and the 4.x OS today, it loaded ok but when I connected the handheld I didnt get the "available update" message I was expecting. weird.

..and as for my carrier, finding the OS or any files on the T-Mobile websites makes the job a thousand times harder

Found this thread... might give it a try ;

JavaLoader Help

Fantastic! that worked a treat.

I do find it amusing how I had to download a 80mb SDK to get the javaloader.exe!

I managed to flash the latest version of the OS... it had 3.8 but now has 4.029 (I think thats it), the display is back... it seems quicker and the email is coming in fine.

Thanks again for the help mate... I'm one happy BB user!