Ok, I've got one of my PC's finally booted up. The problem laid in the Display drivers, which I've now removed. I can now get into Windows.
However, I've created a Network Setup Disk and need to use it so that the Internet Connection on my home network is available to this newly booted PC so that I can use it for browsing the internet, and initially to download New Display drivers.
The problem is though, when I run netsetup.exe on the Floppy Disk, Unknown> has caused an illegal operation and must now close, and also "This operation has been cancelled due to the restrictions on this computer. Please contact your system administrator."