Originally Posted by codprawn
You don't need a DOS startup disk. Assuming you are running XP just boot off the CD - it will ask you about the file system or partition - say you wish to delete it and create a new one. This will wipe the disk and then create a new partition - chose NTFS. Remember you will lose everything!!!
Actually, that depends on the version of the OS and the type of boot CD. Some versions (OEM mostly) of XP will only allow a reload; they will not allow you to wipe the harddrive prior to reinstall.
As said, ideally you want to delete the partition and repartition it prior to reinstalling the OS. This is difficult to do without the proper tools (correct CD for starters.)