Trumpy, it depends how heavily you're overclocked (or underclocked, as the case may be.) Depends a lot on the processor, but 55C is right in the normal temp range.
If you're overclocked, the only temp you have to worry about is at what point your system starts locking up. If that happens, either lower the clock speed, raise the voltage, or put on a bigger fan! Underclocked computers (EG, any computer that's not yet been overclocked) can tolerate quite high temps before locking up.
