Hm. Doesn't seem to work for me:

C:\test\junk>dir
12/11/2010 05:58 7 acentó.txt
20/11/2010 09:46 <DIR> ελληνικά
1 File(s) 7 bytes
3 Dir(s) 236,893,585,408 bytes free

C:\test\junk>perl -E"say for glob '*'"
acent¾.txt
DC44~1

C:\test\junk>perl -E"say Win32::GetLongPathName( $_ ) for glob '*'"
acent¾.txt
Wide character in print at -e line 1.
╬Á╬╗╬╗╬À╬¢╬╣╬║╬¼

(Code tags deliberately omitted to ensure that you can see exactly what I see on my console.)

Conversely, Win32::FindFile does work for me:

C:\test\junk>perl -E"say for glob '*'"
acent�.txt
DC44~1

C:\test\junk>perl -E"say Win32::GetLongPathName( $_ ) for glob '*'"
acent�.txt
Wide character in print at -e line 1.
ελληνικά
ικά
�

C:\test\junk>perl -C0 -MWin32::FindFile -E"say for FindFile( '*' )"
.
..
acentó.txt

ελληνικά
ικά
�