The test case fails sporadically on Windows while trying to overwrite an unused
binary log. The problem stems from the fact that MySQL on Windows does not
immediately unlock/release a file while the process that opened and closed it is
still running. In BUG 38603, this issue was circumvented by stopping the MySQL
process, copying the file and then restarting the MySQL process. 

Unfortunately, such facilities are not available in the 5.0.  Other approaches
such as stopping the slave and issuing change master do not work because the relay
log file and index are not closed when a slave is stopped. So to fix the problem,
we simply don't run on windows the part of the test that was failing.