Solar flares are among the most energetic and explosive phenomena in our solar system. Important information on the energy release, particle acceleration and energy transport can be gained through studies in hard X-rays. The impulsive phase of a flare yields information on the acceleration timing and the magnetic reconnection process. The X-ray spectrum typically consists of the soft X-ray spectrum, emitted by thermal electrons in the flare loop, and nonthermal bremsstrahlung due to flare accelerated electrons. From the spectrum, information on the accelerated electron distribution and on magnetic trapping can be inferred. The particle acceleration and energy transport are important processes to fully understand solar flares.The case study of the 2003 November 3 X3.9 flare presented in this thesis utilised RHESSI?s capabilities, because it is the instrument for solar flare X-ray studies. The analysis showed a shrinkage of the flare loop prior to the impulsive phase, an increase in footpoint distance and an above-the-looptop source. The looptop source is visible up to energies of 50 keV. In the X-ray spectral analysis the emission measure showed two rise phases, explained by chromospheric evaporation. The plasma temperature is between 30 and 50 MK throughout the event, which fits the looptop visibility up to 50 keV. The ratio of the X-ray flux from the northern to the southern footpoint changes from favouring the northern footpoint over a period of equalisation to again favouring the northern footpoint, which may indicate magnetic trapping. The index of the electron distribution function showed a soft-hard-harder development, also consistent with magnetic trapping in the flare loop. The imaging spectroscopic analysis of a second impulsive phase showed a continuous rise in the ratio of the X-ray flux from the northern to the southern footpoint and a continuous hardening of the spectral index.