filesystem corruption freebsd 7.1 release guest on virtualpc 2007/windowsXP host system

[security]

I'm writing this more as a heads up to those using freebsd as a guest
under virtualpc 2007 on Win XP sp3 host.

I created a fixed size virtual disk (8gig). Just to be sure, I ran the
XP disk check on the underlying disk before hand.  I then installed
freebsd 7.1 from cd image.  Next I csup'ed to get the latest updates.  I
then did a make buildworld and a make kernel.  I ran into trouble when
it rebooted and went to run make installworld.  Part way through, I
started getting a bunch of FS errors and then a kernel panic.  I
rebooted and manually fsck'ed /usr.  It did recover, but was unusable. 
I tried the same thing again (fresh install), but I used dd and fsck to
read /usr first to see if I could generate errors. It was clean but died
again while it was writing lots of files to /usr during installworld.

I had my suspicions that freebsd and the XP filesystems we getting out
of sync under a large number of updates.  I rebuilt a third time, but
for this round, I set hw.ata.wc="0" in loader.conf.  I haven't seen any
other corruption since turning off write caching and the installworld
runs clean now (multiple passes).  I'm not sure who maintains the
virtualization pages, but they may want to add that as a suggestion for
virtualpc or other VM's that run into disk corruption problems.

jim