An especially silly mistake.

[Cromdubh]

I have not found any other post which matches my recent bout of stupidity.
I run an iMac, OS X 10.6.4.
I have an External drive, partitioned.
One partition is dedicated to SuperDuper and the other contains my OS on which I keep Disk Warrior and TechTool supposedly out of harm's way rather than an "E-Drive" on my Main Drive
I was rather busy this am,multitasking, forgot to turn on my external drive, popup from SuperDuper, target drive blank, clicked a drive, found later that it was taking rather a long time then discovered that I had selected the partition with the OS containing my DW and TT. I decided it was best to allow the thing to complete its backup and then ran my SuperDuper to the proper destination partition.
I now would appear to have two partitions both containing a bootable TT clone.
I want to clear one to reinstall an OS and my DW and TT programs.
I would appreciate some advice on how best to do this.
I seem to remember that deleting partitions on an external disk in Mac is not straightforward, perhaps especially if it has been "prepared" for a SuperDuper backup .
Thanks in advance.
Tom