The reason you can still retrieve info from a formatted hard drive is this: When you re-format a drive that had data (any files) on it. The actual drive is not erased in the true sense of the word. The FAT is changed and each "pointer" of each sector is changed to essentially show that there is no data stored in that area. However, the data itself is not changed until you re-write over that area with other data. Also, when you utilize a sector on the drive and that file does not fully use the sector(s) then there is extra space at the end of the sector(s) that is called slack space or simply "slack". Portions of files/data can be retrieved from this area as well. I'm assuming that you really don't have any info that the FBI would be concerned with. If you need to keep the typical prying eyes from info on a formatted hard drive, go with any wipe utility and if you are really paranoid, use a govt standard wipe. These wipes usually will fill your drive with a series of 1's and 0's (data) and this will show as useless nonsense to anyone that would attempt to re-assemble the code.