Go to the link above and copy the text (starting from REGEDIT 4 onwards) and paste it in Notepad.
Then in Notepad click Save as. In the box: save as type, select All Files. Then save the file as image.reg somewhere on your computer.
Then back up the relevant registry hive. click Start, Run, type regedit and press Enter.
On the left, highlight HKEY Classes Root. At the top left, click Registry, Export registry file, and save it as ClassesRoot.reg, at a location you remember. Exit Regedit.
Then go to image.reg file. Right click and select Merge. Confirm.
Try and see if the Summary tab comes back (restart if necessary).
If the tab comes back, and image files and programs open correctly (give it some time), you can delete the backed up ClassesRoot.reg file.