Cannot copy files into a HD. Have mac fuse. says is writtable.

hi. i used to have a pc. have an external HD formatted with ntfs. i was looking how to modify it with my mac book and research guided me to mac fuse. a great application that permits macs to modify you external hard disk. after a full day of research i installed all what was requiered and seems to work. i can delete files but the issue is that i cannot add any files. appears a message saying "the operation cannot be completed because you do not have sufficient priviliges for some of the items. i would appreciatte any information about the permissions of my files.
ps: i already tried in the info of the file, setting it up with read and write.

thanx in advance for any info
diego