Cannot Delete Files From Old Hard Drive With Windows Installation

While looking for solutions I seemed to come very close to finding someone with my exact problem, but not quite. Here goes:

I had a hard drive with Windows 7 installed. Everything worked, etc. Got a new hard drive, and installed 7 on there as well without making changed to the old hard drive (prompts displayed during new installation saying "old" windows files would be saved). I've been using it for a while now, however I want to use the old hard drive strictly for storage, so I tried to format it to clear the space out. I got the notice "Windows cannot complete format." Went to the forums and looked thru several suggestions, which brought me to try deleting the files individually.

Included in all this were attempts to give myself (the only user on the computer) full control of all files (which was already the case), to take ownership (via right click options AND command prompt "takeown" and "cacls"), to change permissions/ownership via "properties" for the drive/folders, command prompts to remove the "active" status of the old hard drive, as well as removing "boot" status from old drive (while making sure the new drive had "boot" status), tried everything I can think of using Disk Management AND the DiskPart utility, as well as countless other suggestions that I can barely remember. I'm still getting the "You need permission to perform this action." What I don't get is, if I'm THE administrator (and the only user), how do I not have access to this?

I'm sure there are some details I'm leaving out, but I've been at it for hours. Let me know if there's something you need to know. Running Windows 7 Ultimate 32bit, 4GB RAM, 3.2 Ghz AMD Athlon II.