We will follow Just18 suggestion first and zero the start sector on the drive.
You are now going to make changes several times and with a simple command that is very unforgiving, when you use it once or twice you will be very alert but when you use it several times one gets a bit absent minded it all looks so similar. (I had a scare last night when working with the command I think my finger slipped and I typed the wrong figure and did not notice until I was reading back what I had done, we will not read back what you do unless very necessary.
You must make sure you have a good backup or are prepared to have to reload
I don't expect this will happen but be prepared.
I will assume you have not made any changes and that the USB key is seen as /dev/sdbdd if=/dev/zero of=/dev/sdb bs=512 count=1
The command is saying use the special file /dev/zero
and write the content to the /dev/sdb
Then use KDE Partition manager and set up two new partitions, FAT16 of 100 MB and the rest ext3
For my use post a copy of the new fdisk -l
Follow by installing liveUSB to the second partition.
Now necessary to test it works on the DELL820
Whatever the outcome we will then carry on with the experiment of booting to the second partition with ms boot code.