so I'm wondering what are the differences between a Intel® Core™ Duo and an Intel® Core™ 2 Duo processor? what's the power difference if say both are 2.00 Ghz? and what is 2/4mb L2 cache for?

Lol, did you really have to go to the trouble of putting those TM signs in? :lol:
I think the Duo Core is the older generation of processor. Go for the Core 2 Duo. If both are 2Ghz, the core 2 duo will be faster at that speed. L2 Cache is not so important. A 4Mb cache will improve speeds a tiny bit, but not much unless you are running really demanding applications.

I think the biggest difference is that C2D have a 1066 fsb compared to CD,s 667 fsb. The Core Duos were socket M(mobile devices) and my C2d is socket 775. I'm sure the power requirement for a mobile processor is about the lowest you can find as they are always lookong for ways to extend battery life.

Lol, did you really have to go to the trouble of putting those TM signs in? :lol:
I think the Duo Core is the older generation of processor. Go for the Core 2 Duo. If both are 2Ghz, the core 2 duo will be faster at that speed. L2 Cache is not so important. A 4Mb cache will improve speeds a tiny bit, but not much unless you are running really demanding applications.

:lol: I just copied and pasted the processor names :p

I think the biggest difference is that C2D have a 1066 fsb compared to CD,s 667 fsb. The Core Duos were socket M(mobile devices) and my C2d is socket 775. I'm sure the power requirement for a mobile processor is about the lowest you can find as they are always lookong for ways to extend battery life.

well its for a laptop so I could get a CD T2350 (1.86GHz, 2MB L2 Cache, 533MHz FSB) with 2GB Shared Dual Channel DDR2 SDRAM at 533MHZ, 2 DIMM

or, go C2D T7200 (2.00GHz, 4MB L2 Cache, 667MHz FSB) with 2GB DDR2 SDRAM at 667MHZ, 2 DIMM (about $200 more)

I hear processor FSB is wasted unless it matches memory mhz...

if there is little difference between the 2 in power for say gaming (Civ4 and like games ;) not looking for a high end gaming machine :ar15: ) and other media type stuff than I'm better off going cheaper and upgrading to a new system in the future when needed.

but if the difference is significant than it may be worth it

All the reading I've done tells me your correct about the FSB. The closer you can get CPU and memory to running at 1:1 ratio the faster your system will be. I'm not very knowledgeable about notebooks. For a desktop the difference in power draw between your two systems would be minimal.
Intel's website will probably tell you the power draws of those CPU's. And Tom's Hardware just ran a test that shows differences in memory power usages. It was pretty small even when overclocking but then I look at it from a desktop perspective. For all I know using an extra watt or two will kill your battery fast.

Overall I don't think there is that much of a performance difference(especially considering the extra expence) but there are games that are more CPU bound than others. Its there where you might notice a difference.