Ubuntu 11.04 not booting after dual boot installation with XP

Hii all !!

After days of racking my brains as to how to set up a dual boot system of XP and ubuntu on my RAID 0 Hard disks , I gave up and removed the RAID.
 I installed windows after that on my sda (20gb primary ntfs partition) followed by an u buntu 11.04 on an extended 22 gb partition (20 gb ext4 + 4 gb SWAP).
The rest of the space i left it as primary ntfs partition .I formatted my sdb as an extended partition.

Unlike my previous attempts , ubuntu got installed ( previously it used to fail at the bootloader installation stage).

After installation when i re-booted my system , it directly booted into XP without showing a dual boot option screen !!!

What am i supposed to do ? Do i have to install the ubuntu bootloader again ? In this case is it GRUB or GRUB2 ?

I am a novice to ubuntu and am not that familiar with the terminal ..SO i would appreciate if u r descriptive in ur suggestions involving the terminal .

Thanking all in advance !!! :)

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