You've only got one processor, but some parts of it are duplicated. These are the simpler components which don't produce much heat, such as the main instruction path, the arithmetic unit etc.
It has to report that it has 2 processors so that windows can schedule it to execute 2 tasks simultaneously. That effectively means that with two tasks which for the most part only use the duplicated parts you can get more performance out of the chip.
Unfortunately F@H mainly uses parts which aren't duplicated - the MME stuff and the FPU. These are complex units and produce large amounts of heat, which is why they aren't duplicated. So although you could have 2 copies of the program scheduled to run, in practice they would be waiting for the shared resources to be free.
There's even a down side to HT when you want to run another program, even with only one copy running. Windows sees that it has a spare "processor" which can run your prog, it doesn't know about the shared resources. So windows schedules your prog and doesn't bother interrupting the other FPU/MME intensive prog. If your prog uses the duplicated parts there's no problem, but if it uses the shared parts then it runs like a dog.
Nice one Intel - how to slow down our systems by not thinking out the problem. Nothing new there then. :dry: