I'm running out of idea. I don't really know why it doesn't work on your system. I just check the code...even if something is wrong with the rule file, it would still run (it won't find any map but it would still run). The fact that it couldn't even locate the rule folder does sound exactly the problem we encountered a few months ago (also it was also WinXP pro SP2 too). Denniz figured that problem out on page #31 of this thread.
http://forums.civfanatics.com/showthread.php?t=75992&page=31&pp=20
Post related to that matter:
http://forums.civfanatics.com/showpost.php?p=2618961&postcount=611
http://forums.civfanatics.com/showpost.php?p=2619400&postcount=615
Btw, have you try the older version (6.3) of MapFinder? It doesn't care about the rule directory at all; therefore, it was totally different than version 6.4. If that one does work, then we can go back to figure out why the new one won't recognize the rule directory on your system. There must be something special about that folder in your system. May be Microsoft just introduced another brand new "future tech" that we aren't aware of. Please note that I have stopped using the term "ancient tech", from now on, I will refer to it as "future tech".

Anyway, may be you could try to move that folder out in "c:\mapfinder" or something out in the root directory to see if it makes any different. It it works out on root but not else where, it could be file permission problem....another space age tech from Microsoft to help protect your system.
The bottom line, I just don't know much about all these new feature in WinXP. I'm currently using WinXP Pro-sp2 too, but I haven't yet run into any problem.