According to this article at findlaw.com, "a federal court has just held that an employee did not have a reasonable expectation of privacy in the personal computer he brought to work." It seems that because this employee and a co-worker otherwise had to share a common personal computer, this employee decided to bring in his own computer and connect it to his employer's system. The employer, in this case, was a city government. The employee made no effort to protect any information on his personal computer and left it on and in a public space -- even when he was not at his desk. This failure to password or otherwise protect and guard the personal information on his personal computer eventually led to the discovery of child pornography on his personal computer. That eventually led to the appellate court case that resulted in this decision.
As the article concludes, "if you want to maintain your privacy rights under the Constitution, you yourself must keep your private matters private."
The Kuper Report