curious, are you using a serial ATA or SCSI hard disk or is this a standard IDE disk? actually what is this killdisk program supposed to do?.....what i am thinking is this program actually does KILL the disk.
it might have low level formatting the disk which is why your FDISK cannot detect the drive. when you boot up or in CMOS setup does the BIOS detect your hard disk at all? it should read and list your hard disk model in the BIOS on detection. also i would like the link to your killdisk software.