Here’s an useful little tip!    If you need to find the Service Tag on a Dell, you can get at it using the following command in DOS :

wmic csproduct get vendor,name,identifyingnumber

In fact this command is useful on any PC as it also returns the system identifier, make and model of the PC.

Here’s further information and instructions for other operating systems:

http://www.thegeekstuff.com/2008/10/view-dell-service-tag-and-express-service-code-from-linux-and-windows/