To previous commenters: if you take a snapshot of the entire PC (every file, all registry keys, etc), and then, many days later, you want a report of everything that changed, then naturally temporary files must be created to persistently track the changes from the original snapshot. This app is not meant to be "ultra-small-USB-stick" portable. Not sure what kind of alternative would be possible. Also, if you want to see all changes, and there were 90,000+ new reg keys, it's not the fault of WhatChanged that there is so much output (Richard is right about this). You can choose to view the output in whatever program you want (and Firefox is not a giant text database viewer).

I am also interested in a simple alternative program.
Thanks

I would be interested in hearing about alternatives to this program.

The reason for the huge log files is because of the huge amount of junk in your registry.

I ran into the same problem as Dan, where the program seemed to create HUGE log files. I was actually NOT using this from a USB drive, but from my desktop, and, best as I could tell, the log files it created were so large that it seemed Firefox could not completely load them. It creates one file that lists out your complete file structure (ie, every file you have on whatever drive you are analyzing), then one additional file for each of four major registry keys. For me, it generated log/comparason files of 30MB, 19MB, 9MB, 9MB, and about 1MB. These being text files, they are really, really large, and when the comparison info is attempted to be shown in whatever browser you use, it seemed to me that this was too much for the browser to handle (in my case, I was using Firefox 3, Beta 5).

Will not run under WIN95 as stated. Program "linked to missing export kernel32.dll:IsDebuggerPresent" error flagged when attempting to run under WIN95B.

After trying this program I switched to a different one after this one's portability was brought into question... I believe the problem was it would make HUGE log files quickly filling up small flash drives. Be warned and do some tests before adding it to your portable tool set.