Real bummer that you have to specify the drive letter. (At least on Win7, where I just tried it.)
The behavior is kind of interesting for 'dir' at least:
E:>dir "/"
Directory of \\
File Not Found
E:>dir \\
The filename, directory name, or volume label syntax is incorrect.
Same result for «dir "//"».
(For those not experienced with the Windows command prompt, seeing "Directory of \\" is unexpected, and seeing it means that something interesting must be going on.)