type expand /?
that will give you the usage details. Here they are in all their glory...
Expands one or more compressed files.
EXPAND [-r] Source Destination
EXPAND -r Source [Destination]
EXPAND -D Source.cab [-F:Files]
EXPAND Source.cab -F:Files Destination
-r Rename expanded files.
-D Display list of files in source.
Source Source file specification. Wildcards may be used.
-F:Files Name of files to expand from a .CAB.
Destination Destination file | path specification.
Destination may be a directory.
If Source is multiple files and -r is not specified,
Destination must be a directory.
HTH!