XPS 420 not even getting to P.O.S.T.

Core2 Quad, 3GB, Nvidia 8800GT...

All that happens is the system box seems to start up but with no output from the graphics card whatsoever, and then worryingly, one of the cooling fans starts up and increases its whine until it's screaming - like a jet starting up!

. About  2 weeks ago I started seeing problems with the graphics, so the graphics card is my prime suspect.

It's about 2 years old so likely out of warranty but I'd still like to see if  I could get a Dell Tech out to me (once the weather improves, ofc ;) ) as I'm not physically capable of doing much tinkering with hardware due to disability. 

Further complications are that  the Service Tag for the system is not recognised by the Dell system and also, again due to my disability I find phone conversations difficult.  So what's the best way to arrange a tech visit if one  is needed?

T.