'I installed ubuntu 11.04 after that.Now i am getting SMART failure'
Are you in ubuntu or you can not install any os? If you do not have any OS and can not install ubuntu then try to install windows with full partition (just for hard disk check). If windows shows the same error or can not install then try partition magic boot-able CD and try to low format(delete all partition) your hard disk and just create one partition. Now try ubuntu.
If you can boot ubuntu but showing SMART error then open disk utility. Check all the Drives one by one. Find out the defected drive. Low format the drive using dd command (see on internet).After that if ubuntu show SMART error then sorry for your laptop hard disk. It is really dying. Be ready to buy a new one.