The laws regarding privacy, and computers are pretty open. But basically, if there is marital property, you have every right to investigate it. And that includes his computer. You can hire a forensic computer specialist, which is expensive, or you can have spyware installed (again, legal) and that will catch anything coming up. You wuill not likely be able to use it in court, bec of privacy issues, but check your state -- it may allow for that. But it will give you the info you need to know what you're dealing with, and I can tell you from experience that is incredibly liberating. In your case, if this is the first infidelity, chances may be good that you cna turn your M around. So don't worry that being informed will ruin that. There's such a thing as forgiveness when the time comes.