Dell Dimension 4100 Processor Upgrade Information
compiled by Robert Hancock
These systems use a board with the 815E chipset, and the only matching standard Intel board is the D815EEA. However, the standard D815EEA has onboard audio while these boards do not - Dell probably deleted that option from their version. Another difference is that the Dell version only has two memory slots while the Intel version has three - Dell probably figured that since the maximum memory on the 815 chipset is 512MB, and you can reach that with two 256MB DIMMs, two slots were all that were needed.
You should be able to use any FC-PGA Coppermine Pentium III CPU in these systems (or likely a PPGA or FC-PGA Celeron - but why??) The newer Tualatin CPUs (1.13 GHz and up) will not work on these machines because of the different core voltages and bus signaling levels. Powerleap does have an adapter, the Neo S370/T, to allow use of Tualatin CPUs on older motherboards, but apparently it doesn't work properly on these machines. Powerleap says that they are working on a new version which may resolve this problem.
For reference, the list of changes in all Dell BIOS versions for this system is available here. If you have a BIOS version earlier than A08 and want to upgrade the processor, I recommend you upgrade to the latest version, currently A10.