This problem is NOT solved, it only is concealed.
The problem is caused by an illegal registry hack.
Here the entry for
is not allowed to modify. This must be set to default = C:\Programs ( could be different, related to language version)
(If this is set differently this will cause about 50 other errors/faults not only for jpg.)
Now you can reset to default in
start > control panel > default programs > or see here Annoyances.org - Edit File Types in Windows Vista
The missing icon for the photoviewer is now back again and can be used.
If you want to change your destination for program installation it is ONLY allowed to change
This advise to change the installation destination - change BOTH - was valid only until version XP.
You can find this outdated and now wrong information everywhere in the internet.
Do not set- as one user proposed - to use here "explorer.exe" as THE hack to solve.
If you do, immediately jpg is disappeared.
You no more can correct this!!!!
With the next call of a jpg file this will start every 2 s a new explorer task.
After about 3 to 5 min your system is locked.