We have proposed and implemented User-PC computing (UPC) system as a parallel computing platform using idling computing resources (CPU cycles) in personal computers (PCs) of members in the same organization such as a laboratory in a university. Because the original UPC system has adopted a sequential job scheduling method which assigns new jobs to workers in the descending order of their performance up to its permissible number, some workers may not be assigned any job. In this paper, we propose static and dynamic round-robin (RR)job scheduling methods of assigning a predefined number of new jobs to the workers in round-robin fashion. The dynamic RR method considers the change of the worker's performance by using the CPU time of recent jobs. Our experiment results show that when the performance difference among workers and the number of jobs are small, both RR methods performs well, and when both of them are large, the dynamic RR method shows better performance.