I have a desktop computer running the latest version of Ubuntu 12.04. But it keeps freezing after 2-3 minutes. How can I erase the disk and reinstall? (I already saved all I needed information that I like to keep). Can I boot from a USB key? I have access to another computer for download.
You can boot either from the USB that you mentioned, or from CD. To install from CD, just Download Ubuntu, burn it into a CD. Boot from CD ( make sure you system is set to boot from CD), and follow the installation steps. When you get to the Allocate Drive Space 0r (installation Type),
Choose Erase Disk and Install. To use USB, you can See this site