For first time users who get stuck and didn't make a Nandroid backup
(Note: This method isn't tested thouroughly on all possible Android devices. It should work when a device passes the test implemented in the new versions. Feedback is appreciated)
Some devices/roms don't accept a density change (nothing to do with LCD Density Changer). The result of this can be that your device doesn't boot properly. To get you out of this awkward situation do the following:
Download the file update.zip from *here*. Place this file on the root of your sd card. Go into the restore mode of your device and choose "apply update.zip".
If you don't have a Nandroid backup and you want to be sure you don't get stuck, copy this file to the root of your sd card before you are going to change the density.
To make sure that you always can copy the update.zip to the /sdcard folder of your device turn on usb debugging under Settings->Applications->Development before you are going to apply a density change with LCD Density Changer.
If you are really stuck and the above (general) method doesn't work, here's a method that always will work (provided you have access to your sd card). Basically this method consists of creating a update.zip for your own device that will copy a system file, called build.prop to your system directory.
First search the internet (especially forums) for a build.prop file for your particular device/rom/firmware (If you can't find one, ask people on forums with the same device/rom as you to share their build.prop file from the system directory). This build.prop has to be inserted in your own update.zip package. To create a update.zip with the build.prop I have created a template.
Download the template from here. Unzip the template.zip to a directory. In this directory your will see two subdirectories: META-INF and system. Go to the system dir, delete the file build.prop and copy your own build.prop file to this dir. Go back to the dir that contains the subfolders META-INF and system. Make a zipfile say "my_update.zip" with those two folder as subdirs in the zipfile (basically the same structure as template.zip you've downloaded)
Now your just one step away of having a flashable update.zip for your particular device. All you have to do is sign the zip file you've created and rename it to update.zip. Then follow the above steps to flash this update.zip file on your device.
I will cover the way how sign a update.zip later. For now, search the internet for "sign update.zip android". There are plenty tutorials on the internet how to sign a update.zip file, so... for now I leave it just here.
I know that this method may seem very technical for the average user. I only described this method as a last resort for those people who didn't make a nandroid backup and don't want to flash a rom or firmware (which will always resolve the problem btw). It's just something your can try.
If this still doesn't work for you (which I understand if you don't really into this technical booha) just mail me the build.prop you've found and I will create a flashable update.zip for you. (Email it to firstname.lastname@example.org )