Two High-Count-Rate Gamma Spectroscopy Systems are located at the radiochemistry lab of the Institute of Atomic and Subatomic Physics, Vienna. Those two systems have following names: 'Der dicke Fritz' and 'Der Russe'. Both gamma spectroscopy systems are made up of the following hardware components: HPGe detector, front-end-electronics, a personal computer and an AccuSpec board, which is the key element of the system. Both systems are operated within Loss-Free-Counting (LFC) mode, therefore no dead time occurs. The personal computers are equipped with an ISA slot mainboard and running Windows 98. All measurements are controlled via Genie 2000 Basic Spectroscopy Software and AccuSpec/B ISA card. The aim of this master's thesis is the renewal of the electronics and modernization of the High-Count-Rate Gamma Spectroscopy System. During the thesis, two upgrade possibilities are tested by various measurements using the söcalled twösource-method. The research is focused on resö lution and count loss determination in high count rate radiation systems, so the new systems are compared to the old gamma spectroscopy system. First of all, the applicability of the ARSTech USB2ISA adapter is revised. This adapter is the last element of an analog measuring system. The attempt is to mount the AccuSpec/B board into the USB2ISA adapter and to link the adapter with a new personal computer running Windows 7. The second upgrade option is carried out using DSä1000, where applicability of the DSä1000 is revised by varying the parameters of shaping. The old electronics are replaced by the DSä1000, therefore a digital measuring system is established.