Originally posted by Alvin.C
Also to explain, the reason why you can't format the partition with Windows OS on is because you're currently booted into that partition.
For example as an analogy, you can't swap a car's gearbox when you're driving the car...( gudnuff analogy?)
If you are trying to re-install Windows on a partition which already has Windows on, then format that Windows partition by booting into the Windows XP Setup Disc, entering the Recovery Console, logging in, and typing format x: then hit enter (where x: is the partition in question with the OS installed). Following that, restart the PC, boot back into the Windows XP Setup Disc and choose to install Windows.
Yes, you have to boot from/load up from your Windows Xp cd...
You can format your hard drive as part of the Windows installation process. If your computer is only a few years old and can boot from the CD-Rom drive, simply turn off your computer, insert your Windows CD into the CD-Rom drive, and restart your computer (if the Windows setup does not begin, check your BIOS settings to make sure your computer is configured to try and boot from a CD).
During the setup process, you will have the option of formatting your hard drive; choose that option to erase your damaged/hacked Windows installation, and proceed with the reinstall.
Once Windows is reinstalled, you will have to reinstall your other programs individually from your original install disks.
Unless you have backup you will lose all your data/programs...