Helping people with computers... one answer at a time.
Sharing a computer comes with a lot of potential privacy and security issues. If you don't trust the person you share with, you shouldn't be sharing.
We are two people using the same computer. I used to trust this person until I found out that he had my Facebook password. I changed it, and a second time he was able to get it. I suspect keylogging software. I don't want to open this computer again before knowing what to expect. I read that such software run invisibly and that I can temporary deactivate it when I log in by checking the processes running. I need your help to explain to me what I am about to do. If I stop the process, does it really deactivate the keylogger, and how I can find out which software is downloaded and what to do about it?
For obvious reasons keylogging software falls into the broader category of "spyware", since its very point is to spy on you.
Ultimately, my news for you is not good.
I do have some advice. Unfortunately, you probably won't like it.
My advice is this:
Get your own computer.
Set it up securely so that only you can log in to it, and never leave it logged in when you're not around.
Change every password and every security question to every account you accessed from the share computer.
I know, it's super harsh, but it's really the only solution. Sharing a computer with someone you don't trust simply cannot be done safely.
The instructions that you read sound great in theory: identify the keylogger and disable it. What could be simpler?
The problem is that keyloggers, and spyware in general, have worked incredibly hard to not be found. Heck, an entire industry is built around identifying and removing spyware, and even that industry - as large and as sophisticated as it is - can't remove everything with 100% reliability.
I couldn't even begin to tell you what processes to look for - there are literally thousands of possibilities, and even that wouldn't be an exhaustive list. It's just not that simple.
Yes, you can try anti-spyware software if you like. It may or may not find something. Will it find what your friend has installed? Hard to say. What you probably can be sure of is that your friend will then notice, which I'm sure is also not something you want to have happen by the way you worded your question.
Nope, the only true solution is the most difficult one: don't share a computer with someone you don't trust.