If you can't manage to delete the partition with anything else, get like a Windows 98 boot disk from http://bootdisk.com
then put it on a floppy, and boot from it..
When the A: prompt comes up, enter the following:
Fdisk will launch and show you a menu..
The rest should be pretty explanatory.. just delete the partitions that way, then since the drive is empty.. the XP Home disk shouldn't have a problem..
Caution: Once you delete the partitions, you will not be able to use that computer until you install an operating system..
Thats pretty obvious, but I'm just trying to play it safe so noone makes a mistake.