Cannot Display This Video Mode?

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http://askubuntu.com – Display says "Cannot Display This Video Mode", then goes to login screen. Mouse and keyboard stop working then display goes to blank purple screen. Ubuntu 12.04 installed, was able to login once, hitting tab. Not able to bring up Grub screen. Tried removing nvidia video drivers and installing new drivers. HP Pavilion Slimline AMD 64 Live, obviously very new to Linux and I'm trying to convert computer from Windows XP. Tried the following: display works fine in liveCD but not in full installation Ubuntu 12.04 blank purple splash screen after live install My computer boots to a black scre (HowTos)