absolute system
you can use absolute system from the market, it edits the build.prop and lets you make changes
If you have to ask this you should really also be asking yourself if you want to be getting into something you don't understand. However should you choose to take the red pill then...
1. DO A FULL BACKUP IN CLOCKWORK
2. Install Root Explorer, File Expert or ES File Explorer from market (if one of the latter two enable root explorer option in settings)
3. In your chosen file explorer navigate to /system and locate build.prop
4. MAKE A BACKUP COPY OF THE BUILD.PROP and save it on your SD card somewhere.
5. Open the build.prop file and search for the lines of code in Jan's OP. If they are there then simply edit the values. If not then copy and paste the new code.
6. Save the build.prop file
7. Reboot and hold on...
you can use absolute system from the market, it edits the build.prop and lets you make changes