My experience with Dell is that they will stand behind their warranties, but they suck at actually trying to diagnose the problem.
My sister had a Dell that was fairly new and began having all sorts of problems.....after listening to her describe the problems, the first thing that occurred to me was a bad RAM stick. I posted a thread on here about it, and that was the general consensus, too, that the best place to start was a memory test.
My sister did call Dell and was on the phone to them for TWO days for HOURS each day. Two different people, who, of course told her two different things. The first guy said it wasn't hardware related, it was software, and he sent her to someone else. This second guy told her (finally) that it was something on her computer that was incompatible with SP3. And he said that he would have to reinstall Windows to fix it (said this even though my sister's computer had had SP3 installed on it for months before this problem). Which means my sister would lose everything. All her settings, etc. She has Outlook on there and uses that and the calendar and all for her business, and so that means that ALL the calendar entries and Outlook stuff would be gone.
I told her to mention to them about bad memory, and she did.....she said the techs wouldn't even consider that it might be bad memory or anything hardware related, they insisted it was software related and the only thing to do was reinstall.
If it's a bad memory, reinstalling Windows won't do squat to fix the problem.
She's at her wit's end by that point (their business has ground to a halt) so I get a CD of MemTest86 and drive two hours to her house and run the memory test. Long story short, First pass ended with 35,785 errors. I called Dell and with the first tech I get I told them that I KNOW it's a bad memory stick and DEMANDED they send new. Finally after I actually had to argue with them, they had me run their diagnostic that EVERY DELL comes with that
has a memory diagnostic as one of the tests. 
NO ONE THOUGHT TO DO THIS until I TOLD them it was memory problems because I had just run a memory diagnostic (MemTest86). Of course, their memory diagnostic (which was so simple to run that my sister could have done it and would have saved DAYS of frustration and time!) failed miserably and couldn't even finish the test.
Once the bad stick was determined and I removed it, the computer worked fine. Big surprise. They sent her another stick within a week, so that is good.
So, bottom line is, if you have a decent idea of what the problem is to begin with and can give them a place to start, lol, or run the Dell Diagnostic tests from the machine FIRST, and give them the results, they will immediately stand behind their warranties....but don't count on them to be able to diagnose problems. It's better to come here and get diagnosed and THEN go to Dell support.
