I've got the above laptop which Ive had for about 4 1/2 years.

Recently when I've been using it the power has just switched off with no warning (tends to be if the power lead is disturbed) occasionaly the screen flickers as though theres a bit of a short going on.

Anyhow I think some thing is knakered where the power lead enters the back of the PC. Are the internals of these PC's replaceable, or is it better to just scrap the laptop and get a new one?

Ta

1st guess would that it's full of fluff & overheating – open up what you can & have a blow ?

(you're right, I don't work in IT)

try and isolate it to the laptop or the cable/psu.
do you use the laptop as a mobile or is it kept and used in one place?
if you move it around and can isolate the problem to the psu/cable then just buy a new supply. if the laptop stays put and the problem is with the connector in the back of the pc then you could just tape it down.
if you move it and the problem is with the connector, and you have and can use a soldering iron, then the service instructions can be found on the dell website ( but take a bit of finding ).

try it without the battery in place (i.e. on PSU power only and NO battery in the slot).