Hi:
You can use this free software to delete all partitions and create one partition and reformat the hard drive.
http://www.partitionwizard.com/free-partition-manager.html
You can also try this alternative method of making the Vista install disks if you want to give it another go.
This method requires a 4 GB USB flash drive.
Please click on the link below and then click on the link labeled Windows Reinstallation Guide.
http://philipyip.wordpress.com/dell-community-forums/
Read and follow the instructions on pages 302-305.
I made a bootable flash drive using this method for Vista 64 bit and it worked just fine.