A follow-up to my post from 6 months ago, (concerning the 32" Samsung LE32D400) after I read the recent posts by alejokdj and Niccolo...
To begin with, I would recommend upgrading the TV firmware before even attempting to change any "Service Menu" settings. I got the LE32D400 firmware from Samsung website (release date 7 Nov 2011). incidentally. You need to transfer the data via a USB stick. Be warned, you will probably have to re-tune, etc., etc., afterwards. This upgrade is all perfectly innocent and straightforward. After you've completed the process and you are sure everything works after a full TV "reboot" sequence you can proceed to the next stage. This process is definitely NOT for the squeamish however. You can brick your TV. Honest. In fact, I probably shouldn't even post this here, but I just want to clarify what I did personally. You're an adult and reposible for your own actions.
BE EXTREMELY CAREFUL IF YOU ACCESS THE SERVICE MENU.
I was careless, screwed up the settings and wasted 3 hours returning the TV to normal. I was lucky (some people have rendered their TV useless, or at least had to return it to a Samsung service centre). I believe it also invalidates your warranty too; they can tell you've been tinkering.
As previously stated, to access the Service Menu you should have the TV in standby mode, (ie switch it off using the remote). In quick succession, press "info" > "menu" > "mute" > "power" then "return" (this may be superfluous). You should see the Service Menu after a brief delay. From here on you are skating on thin ice. Ideally you should write down all the settings you can see here, in case you need to revert; don't do what I do, but do what I say! Under no circumstances should you press "Factory Reset" !!! My settings got totally screwed up and the TV displayed an inverted, garbled, almost fluorescent screen image, but I will describe how I eventually succeeded...
Select "Option" & scroll down. I believe there's only two settings that really need changing. After wasting hours with my head upside down (true), I eventually selected Type = 32A6AH0C and Model = LD450. You can press "Return" to get back to the previous screen but there is no "Save" option. Once you've changed a setting, that's it ... there's no going back to what was there originally (so far as I can see). That's why I suggest writing down everything. I Googled this model but couldn't find a list of the recommended settings anywhere. I suppose that's what TV service manuals are for. To continue, once you're sure you have made the relevant changes, you can proceed. As I said, there's no save option, but when you press "Return" on the remote (and can't go back further), simply press the red power button to commit changes.
After restarting the TV, I was successfully able to access and play AVI files from USB. OK, it took a lot of time and heartache but I feel it was worth it. I hope this is of benefit to others. Incidentally, it's possible that other settings may also work. Any further posts here may be of interest. Good luck everyone.