I have a Dell Dimension 9100 with a Intel Pentium D 820 (2.8 GHz, PLGA775) and want to replace it with a Intel Core 2 Duo Processor E8500 (3.16 GHz, LGA775). Is it possible to replace my current CPU with the E8500?
It would depend on the motherboard if it would support the FSB of the E8500 , they are both LGA 775 socket chips and that's a plus but the motherboard could be a breaking point. The problem being that Dell gets to have motherboards built especially for them because they can order such bulk amounts and you won't see these motherboards on the open market because of that.
If you still have the service tag of the computer you an try the Dell customer support and see if they can tell you.
With a normal motherboard I could just go onto a site and look at the board and be able to tell you if it will or not.