One thought at a time.
I just e-mailed the lady in this case, and asked her if she bought the computer new or used, or did someone give it to her. I explained to her the ramifications of second hand computers, but I hope everyone here is already ahead of me.
I urged her to take it to a shop tomorrow and have it analysed.
How Medical Transcription works: In this case, she works from home. She might dial into the client's computer and listen to digital recordings, or someone could deliver tapes to her door, or she could be dialing into a tape machine (mighty unlikely, anymore). [I know these things because my daughter does it, I have been trained for it, and I worked at it in an office where our company computers connected to the client's computers.] Her finished product might have been e-mailed, in the past, but it probably is transfered as a file now.
The files I found included her stock trading files. The number of files was about right for someone that is not computer intensive and doesn't fill up with music or video. Evidently she is on a dial-up connection, because I can't access at night.

Next: I have never done this before yesterday; I'm just a quick study.
I will leave it up to the moderator whether or not to leave the following on the forum.
I was searching for manuals relating to my military surplus electric generators. The search was for Documents, with certain letters at the beginning of the file. This lady's files her work by the initials of the doctor doing the dictation. When I saw files with dates on them, I got curious and downloaded one. I recognized it, and Browsed Host. I wanted to contact her and alert her, but Chat Host didn't light up; naturally, since she had no knowledge of file sharing. [I am thinking that she has some obscure and obsolete p2p on a 2nd-hand computer - it makes sense.] I hunted down the phone number for the clinic that the op notes came from and called. Telling the operator that I had information on compromised patient files got me put straight through to the right person! Nothing like saying the right thing! The OM (office manager) hardly knows which way to push the buttons, but her assistant got on the speaker phone and, when I read them a few lines of the op notes, I had their full attention! They asked for a copy for verification purposes, and to be able to confront the MT. I e-mailed the file. I gave them this full explanation of how I happened to have the info, my personal phone number, and the name of my transcription employer. [I knew that they were legitimate, and wanted to put them at ease - an any good conman would.] The contacted the MT and she called me this morning. I am satisfied that she knows nothing of p2p by any name or activity.
Those of you who have stuck with me through this may now go get a beer.
So it's either malware or a used computer, I guess.
Now, for the "several more". Search for Documents by any keyword. When you find something that looks personal, Browse Host. Sort by Type and focus on txt and doc. Look for the Chat Host button: If it is greyed out, it might be a case such as I just described - Now, I am just guessing.
I reveal this for the same reason the security people tell you to keep your hedges clipped low in front of your windows: So you will know to protect yourselves.
I have no idea what her firewall situation is. If she even knows the word, she probably thinks that it is part of the floorboard of the car. And there is no way that I could ask the question without "How the llll can you be so stupid?" coming through my tone of voice. Even though I have no idea how to prevent this from happening to me.