I dont know what legal issue that you need to have if the computer is in your house. But if you find out the answer to that I recommend other programs then a keylogger, Like 007 spyware. big brother I have heard is another good one. But 007 it can run undected in your puter, besides what keylogg there was it will show you every web site that was visted, every email (web based and any other program) that was recieved or sent, chat room conversations etc… And on some programs if way small monthly fee you can check the activity from another puter. We used it because a friend of ours daughter was raped from a internet prowler and I have kids with puters in their own room, I dont read their mail when I see who it is from but might do some quick scans on some that I dont until I feel safe with the person. But it is there so if for some reason I do feel something is wrong or if they do come up missing then I have somewhere to look
The issue becomes is that she is on another computer. It was one that a friend of mine gave her for Xmas one year. So it is not on my machine and is not considered my property eventhough it is in my house.
This is why I need some legal paperwork. If I do not have this, (I am not a lawyer) but I am pretty sure that this would classify as an invasion of privacy among other things. Unless the laws in NC are different but I do not think so.
But I appreciate you taking the time to look and answer this. But I am afraid that I will need someone that knows the law to help here. 
oh I know that you need some one to help you know the law part of it, I just trying to recommend better programs to use IF you find out the answers to your question.
Sorry that I was not clear enough. I was just trying to give some input on the situation so the individual that may know the law part will have an rough idea on what I want to do and why.
I already have a program selected that I would like to use. Just need to figure out the legal aspect of the situation so I will not get on the wrong side of the law. 
Again, I thank you for the answer. If I need to use something different, I now have a few suggestions.
At this point, I would be just concerned about finding out the truth, no matter what you have to do. If you do find out she is having extra-marital activities, you can always confront her about it. You don’t have to tell her how you found out.
I have to be careful here. Even if I do gain access to her machine, this will bring up an legal hornets nest. This is why I am asking the question that I am asking. If she is not doing anything wrong, then I will see what other things could be causing this. But if she is and I catch her, I want everything that was recorded with the software to be at least admissable in court. I do not think that it will be admissable in court without a court order stating that I can install the monitoring software.
Hello, I have a legal question that I would like to ask and some advice to go about this.
For about the last 2 months or so, my wife is acting VERY strange and out of character. She has not shown me any real affection in the last two months. In that said time, she has gotten cold and starting to seperate things out into hers and mine. She stays up late at nite using chat programs talking to who knows who.
I really to think that there is something going on behind my back and I would like to get the legal documentation necessary in order for me to install a keylogger into her machine. She is not acting like the woman that I married and with her increased time on the computer, ignoring both me and her daughter, this sends up a flag of concern.
Especially she was trying to have other boyfriends behind my back when we were dating.
Asking if she was doing anything behind my back, she says that she is not but it is kind of hard to believe her.
I would like to use such a program to see if she is really doing something behind my back or not.
For if she is, then with the proper documentation, I can use that in the divorce only.
If the evidence shows different, then I will remove the said program and look for other reasons why she may be this way.
If I need to answer any questions, I will be more than happy to. But I am in need of advice.