In August microsoft.com suffered continuous worms, DDoS and other hacker attacks and had to turn to the hosting provider Akamai's Linux server army to avoid the humiliation of being hacked on their own Windows server.
It seems that after hiding behind Linux for a few months, on Nov. 26 Microsoft decided to go back on their Windows 2003 Server and IIS 6.0 in order to show their products are good enough for everyone.
Source
