My DELL Studio XPS8100, eleven months old, was fine for about six months. Then, for no known reason, it would shutdown and reboot. Never a BSOD (blue screen with white letters), sometimes (not often) a black screen (with startup options, e.g., Safe Mode). Three phone calls to DELL Support have resulted in three different approaches to fix (1) download new video driver
; (2) search for spyware/malware; and (3) optimize browser. Of course, since these are all software related (according to DELL), I had to purchase a one-year/four event warranty - I've used three calls for one problem. In a typical day, this shutdown/reboot occurs approx 10 times - most often while playing videos (YouTube, Netflix), but also during Yahoo Mail, and while no one is using the machine. Interestingly, I was able to backup to both Dell Online and to an external hard drive w/o interruption (both procedures took hours - esp after having to find room on the ext HD to back up). Since DELL Support (now, "iYogi") has been completely ineffectual, I am at my wit's end (and long since past my abilities).