The large game issue you described is a classic indicator of the memory problem Civ IV has - Firaxis have now acknowledged it. The patch was put togther by Harkonnen, and does not touch game code (except to include it in the game loader - hardly an issue) so its benign easily installed / deinstalled. Its not a fix-it-all nor is it claimed to be. The effect for many however has been v v good. It has resolved a large number of issues for many people. He is working on a "V2" at the moment. It works by sifting through the memory when the game is running, making it far more efficient, resolving many main memory, video memory and hot card issues. Not working for all of course, so keep expectations on an even level, but his thread is getting a v large number of hits as the word spreads - its running towards 71,000 in 7 days as I type. Worth a go with the symptom you described
Dual boot means you get the option of running a different operating system at start up. Its a good way of keeping your options open when having hassles, and also sometimes a different operating system can help with trouble shooting - or even with games that demand's a particular system you dont usually run. So if you have Win XP, you could give it a go (but if you do, I have to say, what you doing on Win 98

). It is fairly straightforward to do - and once you done it the first time, "the penny drops" and your ok in future.
A slight problem however is that if you are not used to playing with Op Sytems, the first time can produce some nasty problems due to lack of experience, depends on your personal experience and confidence level. If it goes ok, no problem, but, if you get hassles during the loading of dual boot - and you have limited experience - you could get into some nasty dramas. (not terminal, just that in extremis you could end up with a total reload of the whole setup including applications, which can be kind of - interesting - at 3am
Do remember that the game does not support Win 98, so the same must be said of the patch - but some Win 98 Users have reported success, so dont be afraid of at least trying it. The guys on that thread are v helpful, and will I am sure help if you have problemsloading it, and tweeking the fix (scan the thread to see the tweeking involved - its only 2 settings, not complicated)
EDIT : I cant see you loosing much going to Win XP as your main system -its a fair amount of work as you will need to reload all applications, but it really is worth doing as long as your hardware supports it. Can chat on PM re that if you want to try
Regards
Zy
Harkys patch thread:
http://forums.civfanatics.com/showthread.php?p=3447601#post3447601