Few of the large number of personal computers (PCs) in homes and small offices are used continuously. This article discusses a method of utilizing idle PC resources by assigning download jobs to idle PCs and distributing it among them. The requirements for the utilization method are as follows: R1: When a user suddenly starts using an idle PC, he/she must be able to work effectively. R2: When a user shuts down a PC abruptly, the system must continue to operate with any interruption. The proposed method of resource utilization monitors bandwidth usage and avoids inefficiency in users' work. The evaluation results of the experiment system are described. The proposed method requires the existence of a leader PC in a network. The evaluation results of a new effective leader election method that assumes the existence of network attached storage (NAS) are also described.