You're off topic for this forum, which is dedicated to Windows Live OneCare. You may want to try the Microsoft Public newsgroups here: http://www.microsoft.com/communities/newsgroups/list/en-us/default.aspx
However, I believe that your default handler for pictures has changed.
Open the program you wish to view pictures with and use the File/Open command to browse for a picture on the computer. Does it open normally? If so, open Windows Explorer and browse to a picture file. Right click the file and select Open With.... browse to the location of your picture program if it isn't already in the list and make sure that the option "always open with..." is selected before clicking OK to open the picture.
-steve