PowerCMS 2.1.0 will have a folder 'HTMLEditor' in the root directory. PowerCMS 2.1.1 won't (the ckeditor and kfm folders are in the 'webassist' directory instead).
There are probably better ways to tell, maybe a version number somewhere or remembering which one you uploaded.
My method would be to:
1. Back up all my existing local/remote CMS files and folders. (Precautionary)From the read_me.htm file:
2. Back-up/export my PowerCMS Database. (Precautionary)
3. Upload the new PowerCMS files and folders to the CMS directory.
4. Run the installer for your new PowerCMS upload.
5. a) see below b) If necessary restore tables/data from backed-up database (but the paragraph below suggests this won't be necessary).
If upgrading to a newer version of PowerCMS, the Installation Wizard will give you the opportunity to choose whether you wish to copy the content areas from the older PowerCMS to the new one. In order to accomplish this, you must specify the same database settings as were used by the older version.