I have a dell inspiron N4030 laptop 320HDD, 2.31ghz. Dish read error occured

"Disk read error" typically appears when there's a problem with the hard drive, and that problem could be drive failure, in which case a new drive is required.

To check for drive failure, test it with "Seagate SeaTools for DOS" which runs from a bootable CD. Click "Downloads" here and download the "SeaTools for DOS" ISO file: http://www.seagate.com/support/downloads/seatools/ (it doesn't matter what brand the drive is).

Now, on a working PC which has a CD-writer, download & install "IMGBurn": http://filehippo.com/download_imgburn/
Use it to create a CD from the "SeaTools for DOS" ISO file, then boot your Dell laptop from that CD (you may have to go into the BIOS Setup & set CD-ROM as the first boot device).

When your Dell laptop boots from that CD, SeaTools will eventually open. Select the hard drive inside your laptop and test it with the "long" test. If it says "Failed", the drive is no good & needs replacing.