After running the MS Bootvis utility, the file C:\WINDOWS\System32\LogFiles\WMI\trace.log becomes hugely inflated.
The file shrinks on reboting but may rapidly grow to a few gig's in size, to cure the problem run BootVis again and click Trace-->Stop Tracing, the file will now stop growing and may be safely deleted.
The MSBootVis utility may be found here:
http://www.microsoft.com/hwdev/platf...ot/default.asp