Cannot delete files from previous hard drive, administrative issues

Hello!
I have been systematically moving old pictures and other files of value from my the hard disk that used to my primary drive in my old PC. I have now moved everything over and want to delete everything from it making it an empty drive for storage. Unfortunately it seems a lot files are still under the administrative authority of my my previous administrators account. I have tried using an unlocker program and taken ownership of the folders (of which there are now three remaining: Documents and settings, program files, Windows) to no avail. I could of course try booting my system from my old windows xp operating system which should still be intact on the drive, but what use would that be? there wouldn't be a way of transferring ownership from OS to another?

Any Help would be greatly appreciated!

Thank you so much!! That completely solved my problem!