Autheticated user problem

I did not create this group of users at any point and was surprised to find that several of my files in C drive weren't visible today. when I used open in Microsoft word I could however see the files with a lock against them. I saved one of the invisible files on the desktop and in properties --> Security saw that there was no authenticated user group. However, in the C drive files, the ones which are visible, under properties--> security there is the authenticated user group, along with the others such as administrator etc. I dont remember setting up such an account structure. Any help is deeply appreciated.
Thank you in advance.

Thanks for both your responses. These are Word files that i cant see. I just cant understand why access is set for some files and not for others. Since mine is a home computer and i am the only one who uses it, i cant understand why there would be two levels of users, given that all i do is save all my files to the c drive. Is there a way i can make my files visible to me? I read on this board that arbitrarily deleting access causes problems.
Thanks much again!

For instance, i had a file called Lights.doc and had saved it to my C drive. Then the next day I saved another file markets.doc on my c drive. That's when i noticed Lights.doc was no longer in my c drive. I opened markets.doc and hit file--> open and in that dialog box i saw Lights.doc with a yellow lock against it. I clicked on lights.doc and opened it. I then saved it as another lights.doc on the desktop. I can see it there on the desktop but still not in c drive. I rightclicked on the desktop file and clicked on properties. Under Properties-->security i saw access was granted to authenticated users. I went back to the c drive and i checked security under the properties for markets.doc there is no authenticated users there just administratir and maria which is my name for the computer. I hope i am able to explain here clearly. Apologies if it sounds convoluted.
Thanks

sorry for the aggravation! Saving word files now is not a problem, they get saved to C:. But the problem is with the files where access includes authenticated users. In which case I can't see them.
I have Malware Bytes. I will run it. thanks for your help though. I would have called microsoft but they charge for help!