How do you get the path class to accept a windows drive letter?

Suppose I have a dir named c:\Foo, the path constructor throws for every combo I can think of c:\\Foo, etc. I can however, say /Foo and everything works.

Using boost1_33_1, VS 2005, XP Pro SP2 and linking with libboost_filesystem-vc80-mt-s-1_33_1.lib