DIM2400 keps crashing after 30 mins - amber ABC

That combination is not listed in the Dell manual. However, AB is memory and C can be memory.  It could be heat, but first step with the PC powered off, reseat (unplug then plug back in) the memory modules. Also clean out the "dust bunnies" inside the PC while you have the cover off.  Be careful not to disturb the CPU cooler or you will have to replace the CPU heatsink compound.

Forgot to mention the left amber light on the front! I've tried reseating, still the same after 30 minutes or more :-( I'll try replacing the memory - thanx!

BTW - what are "dust bunnies"?

Forgot to mention the left amber light on the front! I've tried reseating, still the same after 30 minutes or more :-( I'll try replacing the memory - thanx! BTW - what are "dust bunnies"?

 jag2jag

This refers to the dust buildup that accumulates inside the case, especially on the heatsinks, fans and the air intake grills.

Bev.

I've brushed everything and put back the old memory but still the same - system starts ok but dies after 30 minutes or so with ABC amber :-(

 jag2jag

For cleaning, it's best to use canned compressed air, this can be purchased from most computer stores, or Walmarts, read the insructions before using.

Did you clean the case/processor fan and the heatsink's cooling fins located under green plastic shroud, also the air intakes located in the front panel, for this you will need to remove the front panel?

 http://support.dell.com/support/edocs/systems/dim2400/en/sm_en/parts.htm 

Bev.