When I try to install Ubuntu 12.04 on my computer and I log in, everything is just... Glitchy, and I have to re-install Ubuntu 10.04 off of a disk I have. This may have something to do with my drivers, as when I tried to turn wireless on it promted me to install some drivers. I didn't, and that may have been my doom when
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Go to System --> Administration --> Hardware Drivers and wait for the list of available drivers to load. When that loads, choose the preferred graphics driver and hit Install. After the driver is installed, restart your computer. When you log in, you should immediately notice some differences.