formatting partition of size more than 8GB fails when done through installation CD

when i tried to format an 10GB disk after booting from installation CD, the format options for FAT, both quick format and other option show formatting succeeded. But in the next step when an attempt is made to create a folder (the \reactos folder), the folder creation fails. Also on rebooting it was seen that the partition on which formatting was done remained in its orginal filesystem (NTFS) and not FAT