XPS 420 Will not boot up

That combination of diagnostic lights isn't in the manual however, a 1 and a 3 & 4 refer to memory problems.  I would try to follow the procedures for those two errors.  Report back with your findings.  Instructions are HERE.

<ADMIN NOTE: Broken link has been removed from this post by Dell>

Thanks the lights are not listed here.  From my further research my issue maybe either 1 o 2 things...either the Motherboard or the Video card.  Beyond that, the documentation that Dell provides is a little sparse.  I follow all the diagnostic guides on Dell Support without any clear direction and/or answers on what is causing my fan to run at high speed, no video on my monitor, and diagnostic lights showing 1,3,&4 and not booting up.  Prior to this issue, I lost video for my built in web cam, so I reboot my machine.  When I did I heard an extremely high pitch noise (like a jet engine starting up) with the symptoms that I described.  Since then the high pitch noise has gone away.  So I am thinking it maybe my video card.  Any thoughts anyone?????

The lights are odd for the 420- they blink in a certain order and then go off after boot. Can be hard to read. Try the memory solutions in the manual.

At this point it could be just about anything, but with no video on the monitor I would suspect the video card also.  Try reseating the video card to see if that helps.  If possible test in another system to be sure.  Along those lines try a different monitor to make sure it's not the problem.  If it's still not working then I would get another video card.  Good luck.

Mary G  - I will give that a try.  My post is correct, I have a XPS/Dimension 420 I bought back 12/07.  The lights come 1,3&4 with out the anything on the video montior, and my fan running at a high speed.  I have 4 Gigs in the unit, but I check to see if memory issue.   I hoping it is a video...maybe now a memory issue instead of the Motherboard.  Thanks for the suggestion.

I have the exact same problem on my xps420.  I bought it in Nov 2007 with the 3 year warranty.  At the beginning of Nov. this year the computer acted the same way as described above:  hi fan speed, lights 1, 3, & 4, no boot up/dell screen.  Because it was under warranty I contacted Dell and they replaced first the motherboard, and then the video card.  It worked fine after that for about 2 weeks.  Then I moved the computer from one room to another and when I turned it on, I got the same exact problems!  And of course now it's out of warranty. 

I too have just experianced this issue, i'm within warrenty so as soon as i know the solution (from dell) i'll re-post!