Should I disable hyperthreading in an Intel CPU?

You have a CPU with hyperthreading technology. You can't change this, but don't worry, you won't have any performance loss; actually it increases your system's performance.

Note that the CPU clock is not equal to CPU performance. The clock is not divided by two for two threads.

Update/conclusion: As already mentioned in the comments, in some (most?) BIOSs it is possible to turn off the hyperthreading. But that will not bring any performance enhancements, due Intels thread management is intelligent enough to use only as much as needed.

Hyper Threading (HT) by Intel is designed to allow two threads to run on a single core at the same time. Thus, since you have a dual core CPU with HT, you can run four threads at once. Generally, the clock speed of the CPU is fixed and does not vary based on how many threads are running at the same time. However, Intel recently introduced a function called Turbo Boost which allows the CPU to run at a higher clock speed if not all the cores are being used. Your CPU has Turbo Boost built in so it will run at 2.26 Ghz if both cores are heavily used and 2.53 Ghz if only one core is heavily used. This is all handled automatically and the difference in clock speed is only about 10% so don't worry too much about it. You will be better off making sure that everything else is shutdown freeing up resources for your main process.