Subject line basically sums it up.  I have a RAID 5 NAS drive that I have basically filled up.  I only have a couple GB free on it, so I tried deleting a bunch of stuff.  The files I deleted are gone, but it didn't free up any space.  And I've deleted a ton . . . 30 GB at least, probably more like 50 GB.  I've completely shut down the drive and restarted it, files stay gone, but still no more space on the drive.   I've run a scan on the array and a disk check (both are built-in utilities accessible through the web interface).  The drive doesn't support telnet or FTP, so Windows Explorer is really the only way for me to add/remove files.  
Any ideas?  I've deleted plenty of stuff from the device in the past and it worked just fine.  There's no built-in trash can or recycle bin that needs to be emptied.  Normally I just delete something through Windows Explorer and the corresponding space is freed up.  This is killing me.  If I have to format the drives and recreate the array I'm ---fouled up beyond all recognition---.  It's 1.5 terabytes.  There's no place for me to back everything up, so I can't format without losing tons and tons and tons of stuff I don't really want to lose.