1.7ghz dual core vs 2ghz single processor?which is faster?

Well it depends on the dual core and the single core processor, not just the clock speed. In theory the 2Ghz processor will run faster than the dual core 1.7 Ghz on applications not designed to run on multiple cores. However, one has to consider that most people have multiple processes running (open your task manager and you'll see you have quite a few). So even though you may be working with one application you actually have quite a few things going on and your dual core may be able to help with that. Also in theory, the 1.7Ghz processor with dual cores should outperform with multiple applications. However, there can be some overhead with having multiple processors. For the most part, this isn't an issue. Throw in many more cores and you begin to have diminishing returns though. So back to your question. A 2Ghz processor may have a faster clock but it doesn't necessarily run faster than a 1.7AGhz processor. There are several techniques that processors employ to increase performance (such as pipelining, different cache sizes, different logic units, transistor layout, etc). So if the cores were identical but running at different speeds then yes, clock makes a difference. If you compare a single core versus two identical cores running together then yes, the dual cores are superior. The Core 2 Duo runs on a totally different computer architecture than the Pentium single core processors. So even at a lower clock and single core they would run faster. The Pentium Duo cores are actually two processors connected and even at a higher clock they run slower than the Core 2 Duo. So clock speed isn't the only thing to go on. Also, the AMD duo cores are better than the Pentium Ds (architecture) but not the Core 2 Duo. Throw in the Core Duo and it falls somewhere in between AND they don't support 64-bit Operating Systems. To further complicate things, processor speed usually isn't the bottleneck. You probably won't notice the difference in 300Mhz anyway b/c your processor will be too busy waiting on the memory or hard drive or your input. In general though, you're better off with the duo cores because they have latest architectures and most people do quite a bit of multi-tasking. I could write a book on this but there are several already from people far more qualified.

well it depends. The guy above is wrong 1.7 x 2 isn't 3.4Ghz. It depends on what OS you'll be using and what programs. If the programs take advantage of dual core processors then yea 1.7 is way better. But most older programs only use 1 processor and don't take the full advantage of the duo core. But like I said most programs today to take advantage of duo core so I'd go that route.

1.7ghz duel core...1.7x 2 is 3.4ghz..faster than 2ghz..simple....And im telling the truth yes duel core does combine processors

The Dual Core CPU cause it can execute 2 applications exactly at the same time if the applications support that! Any single CPU can't do so.