Originally posted by: rorpan
there is quite a list of them

where to start
Aww, the new site makes it harder to find. Tracked it back down. It's the E-Support button on the front of the system. You need to download the Dell Solution center (which will install the driver, but the support center isn't supported on XP). From Dell:
Problem: After upgrading the 8100 system to Windows XP the hardware E-Support will not function as before.
Discussion: Microsoft does not support the Dell E-Support button with either versions of Windows XP Home or Professional.
If a Dimension 8100 is upgraded to the Windows XP OS, the system requires BIOS version XP2 to be used. If BIOS version A09 or any prior version is used, the E-button will cause a "Unsupported Device" error in Device Manager.
Solution: None, the E-button is not supported in the XP operating system. As a workaround use the Dell E-Support desktop version of Dell Solution Center in Windows XP upgraded systems. The system is working as designed, there is
no hardware failure or problem. You can download and install the A02 bios
version and XP version of the Dell Solution software to work around this
issue. Newer versions of the bios should work as well.
A02 bios file: BD81XPP2.exe
Dell Solution Center file: DSC20A01.EXE
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How to disable devices in device manager:
1.Right click on My computer.
2.Click on Properties.
3.Click on the Hardware Tab.
4.Click on the Device manager button.
5.Right click on the device entry you want to disable.
6.Click on Properties.
7.Under Device Usage: Choose "Do not use this device (disabled "
8.Click OK to all open windows and reboot the system.