david, reading you mentioned optimization according to musicXP i decided to not continue because of lack of time.
however i just ha´d a look on their reworked site and found many of the tweaks i thought to remember (a series of registry hacks) have luckily disappeared.
as a sidenote: i don't understand *Turn off System Restore on all Drives* - i would rather be happy if system restore is active on my system drive, although i also switch it off on all audio drives ... anyway
we can't get the few XP64 systems we currently have available to behave as you describe, so there is nothing to investigate and report unfortunately .... the short intermezzo as mentioned above was immediately gone after removing the corrupt sample data.
if you find the time please check out the famous sysinternal tools and keep us updated if you notice something suspicious
http://www.microsoft.com/technet/sysinternals/Processesandthreadsutilities.mspx
christian
and remember: only a CRAY can run an endless loop in just three seconds.