I am not an expert, but I have had the same trouble come up on my machines. As someone else said, reformating normally works but when you try to reformat within the install program for XP, it wont work. So... what you have to do is use another tool or program to get it to work. I have had success formating back to FAT under a windows 98 install reformaing to FAT with a disk partition utility and also by installing Ubuntu. Main thing is, changing the type of disk format. Changing it to FAT or to the lunux version seems to somehow make the XP install see it as a totally new install and let you reformat the drive you want... but if you keep the format the same, for some reason the install disk gets mean and wont do a fresh install. I would suggest downloading a ubuntu CD, install ubuntu linux ( and when you do, do a complete wipe of the hard drive) and then install XP with a complete reformat. Hopefully that will work.