how to completely erase partition/data...fdisk or debug?

I have inspiron 6000 and want to erase the existing data/partition. At the first time, I used windows XP

setup CD for repartition, reformat and reinstallation. But, after finshing the work, whenever

I boot the computer, there's a black screen pops up and ask me to choose which OS I want to use.

It looks like the old OS was not erased.

 

Then, I though I need to do it  by using "fdisk." But, I don't have DOS program including "fdisk."

I am wondering if Dell diagnostics CD has "fdisk." When I searched the tech documents,

all assumed that I need dos program in floppy disk, which is out dated. Also, I heard I can

do it by using "debug command." But, I don't know how to do it.

What I want to do now is to completely erase all data/partition and recreate/format the hard drive

to be ready for OS installation. Thanks for your help in advance.