I've installed ubuntu using live CD. But when I turn my computer on, it starts windows 7 instead of giving me right to make a decision, which OS I need to boot. I think I have some problems with GRUB - it isn't run.
If you installed using a USB then try booting with the USB connected, if you see grub and can boot Ubuntu then have a look at this guide on our website for details of how to resolve the problem. :o)
Let us know if it helps.
Grub organises two OSs on one Harddrive, you seem to have W7 in the harddrive and Ubuntu on a CD - so tell your BIOS to boot from CD.
Step 1 - From a Ubuntu Live CD
Open up a Terminal by hitting Ctrl Alt T; we'll run a few commands.
First, identify which is the Ubuntu partition:
This should return a line like the following:
Mount this partition.
Reboot your computer, this time without the Live CD.
Step 2 - From the installed Ubuntu
If all went well in the previous step, you should now be logged into Ubuntu.
Once again, open up Terminal by hitting Ctrl Alt T.
Now, run this:
This should detect your Windows installation and automatically add it to the Grub menu.
To make the Grub menu show up if it doesn't by default, hold the left Shift key during the boot-up process. You'll then be able to select which OS you'd like to boot into.