Does the internal drive show in BIOS? Killdisk only writes data tot he user data area, overwriting everything on the disk. The windows boot disk should have no trouble with that drive. When kildisk is finished, the drive is excactly the way it is when it left the factory. I do know some of the older presarios had part of the CMOS in a hidden partition on teh hard drive, and blanking the HD would present some issues relaoding, but I haven't seen that in several years. Is your Windows disk an original disk, and is it OEM, retail or upgrade?