cant boot ubuntu after install (first time)

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http://askubuntu.com – Trying to install ubuntu for the first time. I use an usb stick. At partition I use one of the hdd's I have and create a partition of 50gb for ubuntu @ /dev/sda and the partitions name is dev/sda1 with type ext4. All is well and the installation is completed without any errors and I get a dialogue asking me to restart but ubuntu does not boot. I only have one device as boot in my bios and I think its the devide with ubuntu on it since I've not partitioned the other discs. When I create the partition I yse primary type and localtion for the new partition is att the beginning of the space. And (HowTos)