In some circumstances when windows protects a file with a password it doesn't encrypt the file, it just controls read and write access to it. This is the only way I could imagine you had password protected a jpeg file, unless you put it into a zip or 7z archive fail. If you password protected the file by the former method then you might be able to boot up the computer under linux rather than windows, with a live USB operating system, and see if you can open the password protected jpeg then. if you can you could copy it to somewhere, or upload it into webmail as an attachment or something. Then shut down linux, boot back into windows and open the copy/download the attachment copy from your webmail. That would probably work because linux will probably be able to ignore the locking of reading or writing privileges which windows has a password for. If however you've actually encrypted, as in put it in an encrypted archive folder (zip/7z/rar...), the jpeg file then you won't be able to get at it this way.
That all said, I would have assumed that the very fact that you copied the file from one computer (your old one with windows xp)to a different machine (with windows 7 on it) would have already removed the password protection on the file. When windows password protects a file copies of the are usually not similarly protected.
Edited by rp88, 20 April 2017 - 03:18 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB