I had it set up to auto update from MS. So it is possible that a driver has buggered it but it all went pear shaped relatively slowly.
First noticed MCE freezing occasionally, then I had the initial BSOD which said "A clock interrupt not received on a secondary processor within the allocated time interval....Stop 0x00000101."
At least I could boot the machine at that point but it has now degenerated to "Uncorrectable hardware error.....Stop 0x00000124."
This latter stop is apparently very common and not necessarily a hardware issue.
I dunno, Anyone want to buy a shiny silver box that goes "beep"?