Try googling macstories iOS 4.3.1 for a direct link to the files. However if you already have 4.3.1 installed you only need to point to that during the jailbreak process to complete. And yes the location of the file is irrelevant you can browse to it using the JB software. If the files download from macstories as zip it must be your browser as I got them no problems and they're definitely .ipsw. Do you have the link to the iclarified tutorial? Let me know if not as I used that and found it very easy - first JB ever too