I just said my laptop was tough...

Have you tried to clean it ? I had only one Dell laptop and I don't remember if it was as easy as for my actual HP/Compaq where the keyboard seems indestructible and each key can be removed and cleaned quickly. You can find easily Dell laptop keyboards. Here one new for $22.90, and if you buy 5, you will have a 5% discount: http://www.hootoo.com/dell-inspiron-e1505-series-laptop-keyboard-p-1045.html

I would suggest searching online, or continue using the external keyboard you're using right now. Though most external keyboards are universal, all be it bulky tthough. I'm sorry I don't have much to offer in that aspect because by the time the keyboard breaks down then i consider replacments of the unit . However, have you tried turning off the computer, letting it cool down and cleaning out the keyboard? Something could've gotten under the "E" key blocking it's sensior. If that's the case the key will never know when it's been pressed. I've had a few keyboards where a simple cleaning of the system proved to resolve the problem. Even if you're religious about trying to keep clean, over time keyboards can still get dirty.