When 7zip compresses files, it uses all the available cores. This may affect the performance of other applications running at the same time. To reduce the load, you can allot the number of processors that 7 zip is allowed to use. The window that is used to create an archive has an option Number of CPU threads. For example, if you have a four core processor, you can force 7zip to use three of those threads. The last one can be used to run your browser or your instant messenger without any loss in performance.