Having the same problem, over the last few days, with my Studio XPS 8100 as described by cwklint, as well as peteyork in another thread. Fan cycles every 8 or 9 seconds, but only when I'm logged into Windows. Not happening when I was running extended boot diagnostics. I have two questions...
1) for cwklint, did Dell provide any further info related to your comment "Dell tech support said it was a software issue"? What software, I wonder? Theirs? MS's?
2) for RoHe, any further info on your comment suspecting an MS update? Have you or anyone you're aware of tried rolling back updates?
Bummer, cwklint, but thanks.
For you, RoHe, others,... anybody try MS or other update rollbacks? The way the problem has started around the same time for multiple users, in the absence of other system problems, certainly seems consistent with some software issue. I'm tempted to go back to a restore point a couple weeks back, before this all started happening, to see whether the problem disappears.