From: http://support.dell.com/support/topics/global.aspx/support/kb/en/document?dn=1091713

NOTE: In order to complete the following steps, it is required that you to have a CD-R/W or DVD-R/W drive installed on your Dell computer along with a blank CD-R or CD-RW disc.
If you have a portable computer, plug in the AC adapter.

Click the Start button on your Windows desktop.

Click All Programs, Dell Accessories, and then Dell OS Recovery CD.
The Dell Software License Agreement window appears.

Read the license agreement and then click to select Yes, I accept if you agree to the terms.

Click the Next button.
A Welcome message appears prompting you to place a blank CD-R disc into your writeable drive.

Place a blank CD-R disc into your writeable drive if you have not already done so and click the Next button.
The program will create your backup OS Recovery CD.

NOTE: The program can take up to 30 minutes to create your backup disc.

When the backup disc is complete a Congratulations! message appears.

Remove the CD-R disc from the writeable drive and label it Windows Operating System Backup CD.

Click the Finish button.

Congratulations! You have successfully created your Windows operating system backup CD. Store the CD in a safe and easy to find location.