Hi everyone. This is the first time it happend to me.
I installed Ubuntu from web on my windows platform, and when I restart my machine there is no boot menu to select windows or ubuntu. I just boot windows.
I do that a lot of times but this is the first time that I have this problem.

Please help me, thanks

Hi and welcome to LQ.

It's hard to say what happened - perhaps you didn't install grub on the MBR or you installed it on the MBR of a wrong drive?

You could try reinstalling grub from ubuntu live cd.
http://ubuntuforums.org/showthread.php?t=1581099

Thank you for the link.
Now I'm downloading the live cd of my version, and then I'll try to fix my problem.
I have an idea why it happend: One day I "destroyed" my windows boot file (I dont know how to say it) and then I had to remade it "manualy". Probably I changed something and now it couse problems to ubuntu boot.

But anyway I had alwasy Ubuntu and Windows on different drives ad it never coused me this problem.

Anyway, thx again, I will let you know if I was succesfull

Actually I don't know what to do now. I made a little search on Gogle but I found only how to repair booting using Linux.
But I can't even start Linux because it only boot me my windows.
?!?

That's where a live cd comes in. Boot the computer with the live cd in. It should load ubuntu live cd. If it starts booting Windows then you might want to change the boot order in BIOS.

Once the ubuntu live system loads up, try to establish which partition holds your installed ubuntu system. In order to do this, open the terminal and issue:

sudo /sbin/fdisk

(post the output of it here)

All the steps needed are described in the article I linked in my previous post. Look at the "From the live cd" section.

If you are not sure about any of the steps, please ask.

Hi now everything fine!
Thx again man