XP checks the file. When you click on the rotate button a warning message of
picture degradation will pop up if degradation may occur (depending on the
dimensions of the picture in pixels). If no warning message pops up, rotate.
You can do the experiment yourself. Make a copy of the photo (right click on
it, click on copy, hold the Ctrl key down and press the letter V to add
"Copy of filename in your folder; no degradation when you copy this way).
Open the copy and rotate if you do not get the warning message. Rotate it
many times then compare the original and rotated copy on your screen or by