On Win32 I have vienv - Edit local environment variables on Win32 for temporary changes to the environment and CleanPath for permanent changes to %PATH%. It would be very cool to have one directory (from %PATH%) per line in your editor and adjust things there. It'd also be cool if vienv could make permanent changes. Why not combine the two. You could throw up the editor on something like:

=System
ALLUSERSPROFILE=C:\Documents and Settings\All Users
...
PATH;
;C:\WINDOWS\system32
;C:\WINDOWS
;C:\WINDOWS\System32\Wbem
;C:\strawberry\c\bin
;C:\strawberry\perl\bin
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.PSC1
...
WINDIR=C:\WINDOWS
=User
TEMP=C:\DOCUME~1\tye\LOCALS~1\Temp
TMP=C:\DOCUME~1\tye\LOCALS~1\Temp
VISUAL=vim
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