I had problem with deleting EISA partition on several old disks from IBM/LENOVO computers. Usually solutions was to contact manufacturer for some tools but I found this solution on www.mydigitallife.info
Solution is for Windows Vista but it also works on Windows XP.
Here is quotation of solution:
Here’s the trick to delete and remove the EISA recovery or diagnostic partition in Vista. Before proceeding with the deletion action, make sure that at least a set of Recovery Disc Media has been created. Else, you won’t be able to restore your computer to working and factory default condition when any problem on PC requires reinstallation.
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Run Diskpart application by typing Diskpart in the command prompt.
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In the “Diskpart” prompt, enter rescan command and press Enter key to re-scan all partitions, volumes and drives available.
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Then type in list disk and press Enter key to show all hard disk drive available.
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Select the disk that contains the partition you want to remove. Normally, with just 1 hard disk, it will be disk 0. So the command will be:
select disk 0
Finish by Enter key.
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Type list partition and press Enter key to show all available and created partition in the disk selected.
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Select the partition that wanted to be deleted by using the following command, followed by Enter key:
select partition x
where x is the number of the EISA based recovery partition to be removed and unlocked its space. Be careful with the number of this partition, as wrong number may get data wipes off.
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Finally, type in delete partition override and press Enter key.
Once the partition has been deleted, exit from Diskpart, and now users can use the much familiar and much easier Disk Management tool in Windows (diskmgmt.msc) to manipulate the freed unallocated partition. Users can create a new volume (partition) with this space, or simply merge it to existing partition by extending the size of the existing partition.
And here is picture of diskpart
Dubravko Marak Blog 
