you'll have to find the character coding and specify that when you mount it or in the fstab. I have
/dev/hda1 /mnt/win_c ntfs noauto,iocharset=utf8,ro,umask=0 0 0
The iochartset option specifies the charset. I don't know what the available charset are for Greek though. UTF-8 might work if you're using windows XP.
And also, for iocharset=iso-8859-1 and the like, you also have to specify the codepage. E.g.
/dev/hda2/ /mnt/win_d vfat noauto,iocharset=iso8859-1,codepage=850,umask=0 0 0
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