I found several options to use NTFS with read/write premission in Snow Leopard:
1. This one I didn’t tried: http://hints.macworld.com/article.php?story=20090913140023382
2. The alternative method showed in post 1: http://forums.macrumors.com/showthread.php?t=785376
4. Use the ntfsmounter freeware,
The best solution for me was the third.
Paragon 7.1 didn’t do a good work. It failed almost always. The second option I mention allowed to read/write in ntfs partitions. But there was an issue: when I rebooted in windows 7 the files copied to the ntfs partition needed administrative permissions to be modified. I had the same problem with ntfsmounter.
Using osxfuse and ntfs-3g I’ve got read/write skill in osx, and when I reboot in win 7 I can modify the files as a normal user.