I found a very old project here under a CVSRoot directory.
d:\prj\CVSRoot\projectname\
Folder...
.cvsignore.v
filename.v
filename,v.uaem
...
...and so on. There is no CVSRoot folder in the project directory. And only the project folder in the CVS root folder exists. I'm not familiar with CVS. Is it possible to "activate" this project again and check out the latest status?
You don't need anything except already existing CVSROOT directory: it's already a project. Seems you recalled a working copy specifics: it shall have CVS subdirectory in each directory (with files Repository, Root, Entries, etc.) That's not needed for a project itself.
So, just checkout (with d:\prj\ as repository path) and work with it.
OTOH you can consider making a repository from the subdirectory you only need. If so, CVS documentation has enough description of CVSROOT files needed to be a full-value repository.