Interesting. I was looking at NetCraft today, and they report that Wal-mart certainly has an interesting combination for their web server:

The site www.walmart.com is running Microsoft-IIS/5.0 on Solaris 8

Other than the fact that they're obviously hacking with their headers, I can't figure out why. Looking at their other results seems to indicate that they're actually running Apache. Are they trolling for script kiddies running IIS attacks? Or are they just trying to look like they're running new technology?