You don't need to do this straight away!
However if you start getting quite a few symptons of a slow machine, getting BSODs and different errors, then just run a "diskchk -r" from your windows recovery console!
No. Installing Linux is no more destructive than installing Windows.
Windows 98 cannot interact with the Windows NT file system. To install Windows 98, you will need to use a partition tool to divide the hard drive, and then install a special boot manager to load them both.
While windows is installing
I would suggest installing windows on one hard drive, then installing ubuntu on the same hard drive. Use the other hard drive for the backups (partition it).
you can partition the drive.. to use both OS
Yes, if the computer is connected to a network there are options for installing Windows that way.
It depends on type of Windows 8 installer. If it is update, you need Windows OS preinstalled. If it is full installer, you can install it on a bard hard drive.
yes all hard drives must be reformatted before installing an operating system.
After installing a new hard drive in Windows NT 4.0, you should use the "Disk Administrator" utility. This tool allows you to initialize the new hard drive, create partitions, and format them for use. Once configured, the new drive will be accessible for storing data.
If you've reset it, do a windows backup in control panel. Make sure the files in the recover drive are not affected by the restore.
This is likely to be difficult because older software does not always support new hardware. You would need to format the drive and start fresh, or I would suggest installing a new hard drive and installing from scratch. That allows you to recover quickly if your experiment fails.
The glass in the windows will not shatter and the winds can't drive the broken glass (like knives) at people and pets.