It sounds like you have some drivers that for some reason didn't get installed during installation. I'm not sure which drivers didn't get installed but I would say it's irrelevant as you would have no way to install them selectively with no input devices.
If you were able to use them in the live CD then they are supported. I would completely wipe and reinstall 12.04. I would download and burn a new copy of the disk just in case it's corrupted. If you don't want to download and burn a new one you need to at least check the disk you have.
To check the disk boot into the live CD and then press any key at the first purple screen(I just repeatedly tap a key as soon as the boot starts so I don't miss it) On the screen that comes up will be a option to "Check Disk for Defects".
I have Ubuntu installed on a Dell Inspiration Desktop so you should have no problems with you computer so I have to think you have a bad install.
Upon searching the certified hardware I think I found your computer and it's listed so it should work with no problems.....
There were two listed here are the links to the components, anything listed with unknown mean that the manufacturer is not recognised.