You could try searching for the file on the net on another computer, saving it to floppy then whilst computer is staring up, F8 into set up and boot from floppy?
i doubt this will help, just an idea.
Same thing happend to me a while ago, turned out, one of the RAM sticks had come loose. Turned PC off took ram out and in again securly, started up and was fine. :)
I had the same problem with my Wireless network on my laptop, Turned out, it was because i had not entered the network key right on my wireless laptop, which stoped me from sending and responce to the main gateway computer. Hmm