If you're under warranty, contact Dell for a mainboard replacement. If you're out of warranty, give www.aqstech.com a contact - they may be able to repair the mainboard for far less than Dell will charge to replace it (around $700 for replacement, vs. $150 or so for repair).

Good grief, sorry for all the typos. I was trying to type this fast to get this info to you before you did something else!! I hope you can muddle thru what I posted - if not, let me know and I'll clarify things I mistyped!

Most likely you have an overheating issue which inherent in almost every single 5100 sold by Dell. This system has a P4 desktop processor in it which will cause the unit to get very hot. When it gets too hot, it just shuts off, no warning, no nothing. Do a search in this Inspiron forum for 5100 oveheats or 5100 overheating, there are tons of posts about this problem. I would not suggest spending any money on anything until you do a search and see how others have tried to resolve this issue.

If the unit is still under warranty, I suggest contacting Dell. Let them run you thru their silly things to do, without doing them, then request a new "microprocessor thermal cooling assembly" to be shipped to you to replace the old one. Also tell them to send you the instructions they have readily available on how to do the replacement.

I have been thru this twice with my 5100 I bought in June of '03. Replace the heatsink unit twice, most recently two weeks ago and before that in February of '04. Seems like a year before it starts overheating again and just call up and get a new heatsink.

If it is out of warranty, you can do some things to help prevent the system overheating. Get a can of compressed air and blow out the vents to clear any dust or debris that probably has accumulated if you've never done this. Spend $30.00 and buy a Targus Coolpad (OfficeMax has them or you can buy them direct from www.targus.com). This is a high impact plastics "table" that you can sit your laptop on and it raised the back of the computer up enough to allow better air circulation. STOP using the system on your lap, couch, floor, whatever. Sitting the unit right on a soft service does not allow proper circulation. The CoolPad will help immensely and as bonuses, it's small ande compact and swivels too.

I would almost bet your problem is overheating. So any of these suggestions would probably be helpful. Dell is well aware of this problem but they will try to get you to do all kinds of weird things that won't solve the issue. These steps should help. Eventually, if you do nothing, it probably will fry the motherboard.

Thanks for your advice....Bought a laptop chill mat that has fans to cool unit and also shot some compressed air into the vents...so far been on the computer for an hour with no problems...thanks again....keeping my fingers crossed this will work.....seems like lots of people have also had overheating problems

Good. You've taken some steps that should help. I know they all helped mine. Good luck!