Maybe you can use a tool from IBM...
Isn't there something called ZAP from IBM at their page for download od hard drive utilities? After having zapped a drive all partition info is deleted and you should be able to gain access to the whole drive using any common tool for that purpose.
You should be able to find that one or something else here:
http://fdisk.radified.com/delete_partitions.htm
Before zaping the drive make sure you are able to boot it by means of either a floppy or CD and that you can access you CD drive that way - I guess you want to install an OS.
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