Hi, violetmay -
...that it needs the Classic OS9 folder, and then opens up a program called "classic", that has the option to "rebuild classic desktop".
From that description it sounds like you do not have Classic (OS 9) installed on that machine. The 'program called "Classic" ' is probably the Classic pane of System Preferences, which can be accessed via the System Preferences item in the Apple menu.
OS 9-only programs can not run in OSX - they just don't speak the same language; OSX is not written to support those programs.
However, an OS 9 install of adequate version can be used as Classic in order to provide that functionality. Classic is OS 9 used as a program when the machine is still booted to OSX (OSX is running the machine). In this mode, Classic provides an environment in which many OS 9-only programs can be run.
In order to have Classic available you will need to install OS 9.
Your iBook G4 is not OS 9 bootable - it can not use any version of OS 9 as an Operating System. This means it can not use any stand-alone OS 9 Install CD in order to install OS 9.
However, the disk set that originally came with the iBook has the ability to install Classic - this is the only source available for that model to install Classic. It's an optional install, one that must be intentionally selected; it does not install automatically, and probably did not come pre-installed when the machine was new. You should be able to install Classic by booting to the original disk set and choosing to install just Classic.
These articles should help you do that -
Article #HT2431 - Install Mac OS 9 to Use Classic Applications
Article #HT2271 - Using Restore discs with computers that ship w/ OSX 10.3.7 or later
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Some OS 9 programs do not run well in Classic, notably those that require direct access to the machine's hardware. Since OS 9 is being used as Classic (sort of an emulator, though that term is not entirely accurate) and not as an Operating System, OSX (which is the Operating System) retains control of the hardware; programs running in Classic have to go through OSX's Classic interface in order to affect the hardware.
Unfortunately many games are in this category.
Some games have patches available for them that permit them to be run in OSX; Blizzard (Warcraft, Diablo, etc.) is one publisher who has made those available for their games.
Whether the game your son wants to play will run well enough in Classic is something that can be determined by giving it a try.
It may be that you will find it more effective to get an older Mac, one which can run OS 9 natively. There are many used Macs, late model G3 iMacs, for example, which can be bought inexpensively. Since many used machines do not come with their original disk set (they should, but sometimes the seller doesn't care), be sure to get one which can use a retail OS 9 Install CD. This Apple KBase article lists machines which are OS 9 bootable, and indicates which versions of retail disks they can use -
Article #HT1835 - Mac OS 8, 9: Compatibility With Macs
