After windows reinstall, GRUB vanished

[raunhar]

I had Dual Boot system:
Windows 7 with Ubuntu 11.04.
As it happens with Windows, it got corrupt. I had to reinstall it, but now I cannot go to Ubuntu.
I had upgraded Ubuntu 10.10 to 11.04.

How do I bring back the Grub WIndow.
I know this question has been answered before, but am unable to locate the thread.
Is there any Grub installer, by which I can reinstall it.

[mIXpRo]

use this to fix the problem :
http://www.lancelhoff.com/restore-grub2-after-installing-windows/

in case you missed up the grub , install boot repair :
https://help.ubuntu.com/community/Boot-Repair