1. Go to your control panel, and access the device manager. In Windows 9.x that can be found under the System icon. For Windows 2K or XP, open up system management, then computer management. Look for the system devices/resources, and open up that node. PCI to PCI bridge, PCI to ISA bridge and AGP device. Depending on your chipset, not all of the above maybe present. For each, open up the properties and check the drivers tab. When the driver info states 'Microsoft' as the creator/supplier, it's ok. When it says 'VIA', you have the 4in1 drivers installed.
Do the same for the IDE controller. That one has it's own node. Normally it should list 3 items. One represents the IDE controller itself, the other tho merely the promary and secondary channel of that controller. Don't bother with those, as they cannot be checked/updated. Only the IDE controller itself is relevant.
2. Deinstallation can be done from the same properties tab. Press the 'update' button, don't let the Wizard search for drivers, then select the component that is most generic/default, and is supplied by Microsoft. That will uninstall the current driver, and replace it with the one you select.
What do they control? The AGP driver controls the AGP interface/pipeline in the north bridge of your chipset. The IDE controller the interface to your HDD/CDROM/DVDROM/ZIP. The PCI to xxx bridges control the various interfaces in the southbridge of the chipset.
3. Straightforward? I should think so, if you follow the above steps.
4. Regarding the CPU fan operation. If, on an Athlon the CPU fan would not operate correctly or worse, would fail alltogether, the CPU would overheat within seconds, resulting in a CPU core meltdown. After that, your Athlon would be dead, and your PC would no longer boot. Since the PC in question only freezes, one can assume the CPU cooling fan still operates normally
Jan Peter