Could not Initialize Photoshop: Locked File

Hi everyone,
I'm quite confused with this error. Is the Properties command the one you see when you left click a file? Or is it somewhere else? And can anybody please tell me exactly what file I am supposed to unlock. Thanks so much, your help is invaluable!

Adobe Photoshop CS3 Extended
Could not initialize PhotoShop because the file is locked.
Use the ‘Properties’ command in the Windows Explorer to unlock the file.
OK
