No they are not gone the best you can do is smash up your disk and melt it down
If you don't want destructive forces attacking your hard disk use the Royal Canadian Wipe, DoD 7 Sweep, or a Gutman with Gutman being the preferred method of the above. But yes the data can still be restored.
To do so I recommend: Darik's Boot and Nuke
- Linux Kernal Based Live CD
- GNU Licensed, Open Source, Free
- Does all of the methods listed above and a few others
- Can be set to do another swipe automatically after the first one is done
- ISO file is only 37 or so megs
- Once Program has started you can remove the CD and let it continue Nuking
- Works with FAT16, FAT, VFAT, NTFS, ext2, ext3, reiser, and other file types
http://dban.sourceforge.net/