[ubuntu] Can't boot computer after installation from USB Drive

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http://ubuntuforums.org – Ok, so I was testing out Ubuntu on my old computer using a USB flash drive, and there was an install button. After testing Ubuntu, decided I liked it, I opened up the installation program, installed it, and rebooted. Somehow, even though I didn't set it to, it replaced Windows XP (Which is OK I have backups) with Ubuntu, but whenever I try to boot from the internal hard drive (which is where it's installed), it just has a black screen with a blinking white dash at the top-left corner of the screen. It justs stays there forever. Did I do something wrong? Please help. Thanks. (Hardware)