Problems removing disk partition

It looks like I screwed my drives up pretty well this time. I would like my HDD to return to the way it was when I first took it out of the box so I can do a fresh install. I'll give a short rundown of what I have done so far:

1. Originally had 64GB SSD with windows 7 - worked great. (C drive)
2. Added 2.5TB HDD as storage - worked great (E drive)
3. have z68 mono - attempted to merge two drives using Intel Smart Response Technology - HDD disappeared (no more E drive)
4. went into Biostar RAID configuration built into boot sequence and deleted all raid partitions - lost all OS
5. created new raid partition - showed up as 280GB partition
6. tried to install OS - caused windows 7 boot loop
7. physically unplugged HDD, went to Bios and switched back to AHCI - reinstalled windows 7 on SSD
8. went through all driver installations and seemed fine - until i attempted to update the Bios with Biostar's online bios update utility.
9. system reset itself - windows blue screen of death - followed by boot loop
10. unplugged SSD - plugged in HDD - attempted to install windows 7 - bios shows 2.1TB partition and 280GB RAID partition.
11. confused because RAID has been turned off since step 7 - windows installation will not allow me to delete 280GB partition.
12. Opened command prompt and did 'diskpart' command followed by 'select disk 0', followed by 'clean all'.
13. current state - command prompt cursor under 'clean all' is flashing - i assume its taking a LONG time to clean the 2.5TB partition.

Any advice would be greatly appreciated.

Thank you