The last thing you expect your laptop to do is shock you…literally. The CNET team learnt it the hard way; they realized that the tingling sensation at their fingertips was not a bout of some medical condition but the result of an electric shock from their Dell lappie. The charge varied from "a gentle tingle to a sudden jolt." Apparently not all Dell lappies shock you but brushed-aluminum finished ones namely the XPS M1330 and XPS M1530 are the culprits. It is believed that the shocks are the result of a power adapter that isn't grounded properly because its 2-prong connector lacks a third pin. It may be noted that Dell's knowledge base recognizes the problem in an entry entitled " A Tingling Sensation May Be Noticed When Touching Metal Components of Dell Devices Equipped with Two-Prong AC Adapters." The entry also states that "the voltage (tingling sensation) does NOT present any risk of injury to the user."

Dell got in touch with CNET and has offered to replace the two-pin power supplies with a three-pin version if requested to do so. Entries on Dell's forums suggest that problem persists and incase you belong to the unlucky group then get in touch with your nearest Dell centre.
Source