Need a little Mac Help

I bought six storage units at auction this week. One of them contained a Mac all-in-one. The machine is working and I wish to resell it. I got into utilities and reset the password. Good so far. I'm wondering what else I should do.

There is an option to reinstall the Mac OS X. Not sure if that will lead to any problems.
There was mention of a keychain password. But I think more importantly, I just need to get a clean OS on here to protect the previous owner's privacy.

So what can I expect if I try to reinstall the OS through utilities? I do not have a disk.

Not sure but I would expect it to put it back to "factory fresh".

I use youtube videos to assist me in figuring out how to on computers. It does not always work but worth the effort. In small letters/numbers there is a model number and it should start with the letter "A". Enter that into the youtube search box. Do the same with OS X. Watch some of them and you should be able to accomplish your goal.

One of the advantages for me using youtube videos is that I can play the video while I'm doing the action/repair etc. If I need to I can pause and back up the video. 73, Mike

The only sure way i know of protecting the previous owner's privacy is to install a different hard drive that's been wiped & tested, and then do a OEM install of the operating system. It depends on which OS it is .... but i think they're available from Mac for a pretty reasonable price. It's a small investment, but then you know the job is done right. It's also the simplest and easiest way too.

Keep the original drive on hand for a little while. Once you know you won't need it anymore you can either wipe or destroy it.( If opt to wipe, make sure to nuke any hidden GPT partitions that might be on the drive as well.)

Edited to add: It's just an opinion, but the re-install options are nice when you've got a problem with the operating system that you don't want to spend hours (or days)on. They're not so great for data security.You can tell because a fresh OEM install will take up a certain amount of space on the drive. A reinstall will often be two or three times that size. It's got to be carrying a lot of data over from the old to the new.