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Do you have original CD or recovery CD with you. If you have Recovery CD then boot  on expert mode and format your hard drive with clean installation. If you have OEM CD or DVD then change boot
sequence to boot from CD first and format your computer with clean installation. If
you failed both methods then download fedora Linux
(download.fedoraproject.org/pub/fedora/linux/releases/10/Live/i686/F10-i686-Live.iso)
and burn as bootable CD. It automatically loads in your pc then you can format
your hard disk. After fedora installation, either you can make dual boot installing
windows on free space or  you can
override it installing windows.