I am first worried that you are not starting your computer on that repair disk. You must start pressing the F12 key about once a second as soon as the computer starts. That should bring up a menu that allows you to choose to boot to the DVD drive. That
should lead you to options that may work.
Your hard drive could be failing, but lets assume not and that it is simply so corrupted it can not begin.
First choice is a Factory Restore
Press Ctrl+F11 during the Dell screen
You will lose everything on the hard drive -- EVERYTHING
It will re-install exactly what was there when you started the computer for the very first time.
If you have data that is not backed up, you need to find someone that can externally mount the hard drive from your computer to another computer and read and copy as much data as possible on to some other media which you will be able to copy back on to your
computer once it is re-built.
It is also possible the hard drive hardware itself is failing or has failed. When you take that drive to someone else with the know how and equipment to copy the data, that person can download the hard drive manufacturer's drive tester software to see if
it is failing. If it is failing and you need to replace....
You will then be forced to do a clean install from your Windows 7 install disk that I hope you got from Dell. If you did not, you can probably get them to send you one for a small fee.