I'll be going to the UK in a few weeks with my D400.  I know, of course, I need a grounded (3-prong input) plug adapter.  The Dell knowledge base says the AC adapter can handle current worldwide, but then suggests the following: 

Before using AC power in a foreign country, you may need to obtain a new power cable that is rated for use with the level of electrical voltage in that country. The power cable supplied with Dell notebook systems sold in the United States is rated to handle 115 volts.

Do I need a different power cable or just the adapter.  Thanks in advance for the help.  Larry