Delete files in empty space

Hello

I just scanned my Macbook pro harddrive using a Data rescue software and i saw that there were a lot of files i deleted long long back still turning up and i could recover the same if i wanted

That would mean that they are somewhere on the drive right.. is ther any way i can delete them cos basically its sensitive stuff and i wouldn want anyone accessing it in anyway not even data rescue...

Thanks

Boot with your install DVD and use Disk Utility to wipe free space. It will give you a choice of how many passes. Be aware, however, if you choose 3 or more passes and the drive has lots of free space, it can take a considerable length of time to complete.

And one more tip: Before doing the above, make a backup of your hard drive.