See the section titled "Using Dell PC Restore by Symantec" at the bottom of page 131 of the "Dell Inspiron 1720 Owner’s Manual":http://support.dell.com/support/edocs/syst...df/DT549A00.pdf
or, if you don't have a PDF reader:http://support.dell.com/support/edocs/syst...20/en/index.htm
From what I read there, it will return your computer to the state at which it left the factory. There are also other sections in that area of the manual that describe other methods of restoring your system.
The section "Restoring Your Operating System" begins on page 130 and describes 3 options to accomplish this. The one I mentioned above is the second of those three options. From the contents of your other thread here (Why did you start a new thread?), I think that might be the best place to start.