Thank you for your post.
It is the files with the extension .rgd which contain the enviromon data, they usually are named with a long number. Unfortuantely they are not saved in an ASCII format and so you cannot open them as a text or read the data in them.
The best way to get data from them is via the Enviromon software in the spreadsheet view - you can copy all of the data out and into Excel.
Hope this helps