I had the same problem with mine, no matter what I tried I couldn't find the firmware file. that was untill I came on here
What I did was, I went into the control panel of my pc (XP) and into folder options and changed the setting so it would show all hidden files. I then went into the search function on my pc and put in ispw and made sure it was set to search all files, hidden as well and it found it. I then moved it to a folder on my desk top.
Hope this helps
Cheers