Hi, I am having similar issues. Unfortunately, when I bought this comp. in 2008 it only took 5 months for it to crap out. Tech came out twice, finally replaced motherboard and video card. This week it finally crapped out again. Took it to Staples, tech said 'don't waste your time and money on working on it as it is an ongoing issue that Dell doesn't want to acknowledge, and people are even filing lawsuits for faulty parts, etc.'
From reading online in several forums I have read many suggestions though...one says to 're-seat processor', another says to 're-insert video card', another says to 'replace motherboard'. However, I am told that the motherboard must be ordered from Dell.
Was online 'chat' with 2 Dell service reps. (foreigners I presume, as their English grammar wasn't so hot). They claim that the xps 420 has 'no known issues with the motherboards.' What a load of crap!
This is sad because I have had a Dimension system since 2002, with no problems and just 'won' a Dell mini notebook computer.
I am at a loss as to what decision to make...Scrap the xps 420 and buy a substitute unit AND send off a written complaint to Dell, OR take my xps into a shop and take my chances.
~signed....'fed up' lol