lion can't continue installation process

hi guys, I have a 2011 MacBook Pro. I'm trying to reinstall Lion from an installation dvd but i get this windows saying that my hard disk is locked. i tried the "chflags nouchg /Volumes/volume" commands to unlock it in the single user and then fsck -fy command to repair the disk but i get this:
** /dev/rdiskos2
** Root file system
Executing fsck_hfs (version diskdev_cmds-540.1~34).
**Verifying volume when it dismounted with write access.
journal need to be replayed but volume is read-only
**checking Journaled HFS Plus volume.
The volume is Macintosh HD
Invalid extent entry
(8,0)
**The volume Macintosh HD could not be verified completely.
/dev/rdisk0s2 (hfs) EXITED WITH SIGNAL 8

I dont know what to do, pliz I need help

Can you access Recovery? Boot and hold down Command-R and access Disk Utility that way. Did you burn the Lion DVD yourself from an original App Store purchase? Would have thought with a 2011 model Lion would have been the system it came with so you would not get a DVD originally.

Have a read of this link:-

http://support.apple.com/kb/HT4718

Early and Mid 2011 MBPs and iMac came pre-installed with Snow Leopard 10.6.6 not Lion. That's the way my Mid 2011 iMac came out of the box. (Purchased May 2011.)