Dell Inspiron 660s dead as a dodo

I can't imagine what a virus could do that would fry a motherboard and power switch ... formatting the hard drive and reinstalling is the best course of action ... nothing you have said even leads me to believe there is malware on the machine at all.  

If anything it sounds like a power surge killed it.

Me neither. I'm starting to suspect that the guy was just trying make a case for charging us £79 a year for a software warranty. He was very pushy just like a desperate salesman apparently. Do they work on a commission basis?

Having now booted into the full Windows environment I can see now why he was so insistent that we only ran it in safe mode - the screen goes from desktop to black screen to desktop before going black permanently. It does look like an OS re-install or maybe restore to factory default will be necessary, but not because of any virus infection. I've now scanned the system for viruses, rootkits and other malware with a variety of tools and it's returned a clean bill of health. The engineer wasn't prepared to carry out a proper fix because only the hardware is covered by the standard 12 month warranty.

When I rang tech support this afternoon to find out exactly what the engineer had done I got the same hard sell technique and couldn't get a word in edgeways. I'm very tempted to make a formal complaint.

If the OS is Windows 7, I suggest a clean install of generic Windows. You can download the install disc ISO from Digital River.

It's easy to keep these machines operating smoothly, and that's where I would start.

Thanks for the advice. I did this using a USB thumb drive, got all the drivers installed from the original CD and then rebooted. I'm now right back at square one; I get the error message "display driver stopped responding and has recovered, display driver Intel Graphics Acceleration driver for Windows 7 stopped responding and has successfully recovered". The screen then goes black, returns to the desktop, goes black again before finally returning to the desktop and freezing the system.

The engineer kept telling my mum that the problem was that the computer has no graphics card installed, yet I was under the impression that it shipped with an "NVIDIA® GeForce GT 620 1GB graphics card". What on earth is he talking about? Does he even know himself? This is the model listed under the GPU section of the device manager so it's been correctly installed. I even tried uninstalling it in the hope that the system would fall back on the HD 4000 chip instead, but the issue remains. All the engineer would suggest is crossing his palm with £79 and he would fix it on the spot, and otherwise it wouldn't be covered by the hardware warranty. This issue didn't exist prior to him replacing the hardware so surely he is liable for fixing it?

It would be nice if I could get an official response from Dell because I can't believe this is acceptable practice, or that this is the kind of behaviour Dell's long-standing good reputation for customer service was built on.

Have you installed the latest drivers from Intel's download site?

you might go to the dell support site and try to download the driver from there also.  there is also a way to let windows 7 go to the web and look for a driver from the windows "device manager".

No, I've only tried the drivers from the install CD so far, which no doubt are a bit out of date by now. The problem was without network drivers being installed I couldn't get on the web at the time. Anyway, it got late and I had to get back home because I had an early start the next morning. I'll try your helpful suggestions next time I visit, thanks.