Breakdown of personal computers is a common problem experienced by many computer users in Nigeria. Breakdown could be due to anomalies in the functioning of some hardware components, conflicts in the execution of software elements, and/or negligence on the part of users and unskilled computer maintenance personnel. Failures or breakdowns impart differently on different users. A thorough understanding of the causes of failures and maintenance steps that users can carry out on their systems to avoid or reduce breakdowns are discussed in this paper. To identify major causes of breakdown, the survey method of data collection was adopted to elicit information from computer users who responded to questions contained in questionnaires administered to them. It was discovered from the analysis of the data that virus infection, unqualified maintenance technicians and local socio-economic/environmental factors are the major causes of computer breakdown in Nigeria.