I have an HP / Compaq dc5700 PC currently using Intel Core 2 Duo E6320 that I want to replace with an Intel Core 2 Duo 6700. The switch is so I can meet my video processing software requirement for processor speed. Good idea?
The E6320 runs at 1.8Ghz.
The E6700 runs at 2.66Ghz.
Both of these CPUs where options on the Compaq dc5700 when it was sold and they use the same socket. So there should be no risk of BIOS compatibility issues and the PSU should also be OK. They are also both rated at 65W TDP by Intel. So your existing heat sink & cooling should be OK. (this doesn't really make sense as the E6700 will surely be slightly hotter and use slightly more power, but oh well).
Speed should increase significantly for CPU tasks. But you might find the rest of the PC (disk, RAM) etc.. still makes the machine feel slow by today's standards.