Ok now to truly wipe that hard disk clean.
You can use that System Repair Disk you made or you can use your Win 7 on the USB/
With the System Repair Disk:
Boot up from the System Repair Disk and choose Command Prompt from the menu you get.
With the Win7 USB/DVD, boot from it and when you get to that first dialog asking you to hit the Next key, use Shift + F10 key combo to get to a command prompt.
The command prompt will be X:>
You actually have a mini-version of Win7 at this point loaded into ram dr8ve assigned the drive letter X.
You will use the DiskPart program now.
For the following enter the command shown and then hit the Enter key after each one.
List Disk This will show disks on your system
select disk 0 (assuming 0 is the numeral assigned to your hard drive)
detail disk (this will help confirm that you made the correct selection)
clean all (will write zeroes to entire disk--get coffee, this will take awhile)
exit (after the clean finishes. will exit from DiskPart)
exit (will exit from command prompt)
A format does not overwrite your disk.