Repair ubuntu 12.10 installation

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http://askubuntu.com – I installed ubuntu 12.10 lately. But some problems seemed to occur. Brightness control not working. Mouse flickering randomly. I downloaded a newer version of ubuntu 12.10 and after booting it as live found out that these problems is fixed in that version. I found out that some files like sys->class->backlight was empty in the first one. How can I upgrade my current installed version with the newer one or repair it using bootable disc of the newer version, so that I dont need to reinstall all the softwares. (HowTos)