I was backing up my user folder to a flash drive. Saw it was backing up a lot .dat files (normally started with a letter followed by a long string of numbers. Went back to user folder and searched for *.dat files and only found one. When copy was complete, I searched and found all those files. What is going on? I do use show hidden files in my folder icons. There is a second discrepancy on size of folder. Properties say 1.86GB, but looking at contents, it only adds up to tad over 1GB. Most of the size is in AppData\Local. Seems to be an awful lot. Any suggestions how to clean that file?