Running test suites under Windows 7

[Walter Bright]

When I first installed Win7, I was having problems with erratic failures to 
write executable files while running the D test suite. Eventually, I discovered 
that Windows Defender was the problem, as it tried to do a virus can on every 
exe the test suite produced.

Turning off WD helped a lot, but I still got those failures every once in a while.

I have since discovered that "Microsoft Security Essentials" was doing a "real 
time scan", mucking things up. That has to be turned off, too.