[Bug #2369] ENV's strange behavior on WinXP

[Usaku_NAKAMURA]

e$B%A%1%C%He(B #2369 e$B$,99?7$5$l$^$7$?!#e(B (by Usaku NAKAMURA)

(e$BC1$J$k%a%b$G$9e(B)

Vistae$B$G$bLdBj$J$7!#e(B
e$BBP1~$9$Y$-$+$I$&$+HyL/$K$J$C$F$-$^$7$?!#e(B

http://redmine.ruby-lang.org/issues/show/2369