Thanks for your reply. My computer is a MacBook Pro with OS X 10.7.3.
"Preview" is my default app for viewing graphics files. Once it's been launched, it opens selected files promptly. But if Preview's not already active when I click on a graphics file, it takes 45 seconds to launch.
I'm supposing that Preview application's been corrupted, and that if I can install a fresh version, that will fix the problem. So I'd like to know how to find a replacement.
No install media came with my Mac. It was explained to me that the hard drive was partitioned, and system reinstall software was in the separate partition from which it could be accessed if a reinstall became necessary. But I don't know how to access this replacement system or in particular how to access its components, specifically "Preview".