I used to have a D600... work just upgraded me to a Toshiba M4 last week, thank goodness.

Anyway, I had a cheapie Targus adapter that I picked up for about $25 off eBay. It gave me a warning about the power adapter not drawing enough power when the computer booted up, but it always worked like a champ. Similar to Oceanrider's experience, my laptop never charged while it was on the charger... but it never drained, either.

My husband has some sort of Inspiron, which came with a Dell power adapter for planes. It has the same plug as my Latitude D600, and his power adapter does charge the battery. So I know it's possible . I still preferred my Targus adapter, because it was a lot smaller and lighter.

My husband also used an APC adapter for a while, which had an actual AC plug. So you could plug anything in, including a laptop... he's also used it to run external hard drives, charge camcorders, etc. Again, I preferred my Targus adapter due to size.