This paper presents fault-tolerant simulations of a single-writer multi-reader regular register in storage systems. One simulation tolerates fail-stop failures of storage servers and requires a majority of nonfaulty servers, while the other simulation tolerates Byzantine failures and assumes that two-thirds of the servers are nonfaulty. A construction of Afek et al. [3] is used to mask semi-Byzantine failures of clients that result in erroneous write operations. The simulations are used to derive Paxos algorithms that tolerate semi-Byzantine failures of clients as well as fail-stop or Byzantine failures of storage servers.