Installing Ubuntu 12.04 LTS hangs on purple screen

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http://askubuntu.com – Ive been having trouble installing Ubuntu on my system. I tried from CD and from USB stick. It starts to go but eventually the little dots underneath the word 'Ubuntu' stop changing colors. I've let it sit there for at least an hour to make sure its not just taking a long time - nothing changes. I had ubuntu on this machine a couple of months ago but my HDD crashed that had it on it and so I removed the hdd and put a new one in. When I went to install this time - it hung. So I diagnosed my PC and found out my CPU was overheating. So I fixed the overheating problem and also threw in an olde (HowTos)