I recently decided to change from using windows xp on my dell dimension 1100 to Ubuntu 12.04. I followed the instructions for making a bootable USB stick and even managed to run abuntu from the USB to see what it was like before deciding whether or not to install it fully. My problems started when I tried to install Ubuntu. I went through all the screens choosing language, location etc. but when it came to the screen with the Ubuntu logo and the 5 dots turning red to white nothing else seemed to happen. The light was still glowing in the USB stick but there seemed to be no hard drive activity. I left it overnight (7hrs) but it still had not progressed come the morning. I pressed the escape key and was presented with a black screen with lots of white writing on it. The last line says "Begin: Configuring screensaver... ... done." I left it again until I had returned home from work but the same problem remained. I switched off my computer, restarted it, then tried the install from USB option in the boot menu. This time I did not get the pages telling you about all the features of Ubuntu but it stopped again at the same place as before. What have I done? Probably something obvious to someone with any type of computer knowledge could help with, but for now I am stuck with a PC with no operating system. Help me please.