My computer bombs whenever I launch my MajorSoft WordMangler program. 
If your problems occur only with one particular program or action, and are fairly repeatable, they should be easy to fix:
Try giving the program more memory. Be sure the program is not running, then click once on the icon of the program and press
-I (Get Info). On newer systems, choose "Show: Memory" from the pop-up list. Increase the "preferred" memory size by 25-100% and try the program again.
Check the vendor's web site or http://www.versiontracker.com for updates or patches to the program, and try installing them. You may have a known problem that has already been solved.
Try starting without extensions. The vendor will tell you to do this, so try it first. Hold down the Shift key while the Mac starts up. It should say "Welcome to Macintosh (or Mac OS), Extensions disabled." If the problem is gone, see the next question and answer entry.
Quit the program, and then delete any preferences files used by the program. If they are complicated preferences, copy them to another folder or a disk in case it turns out they're not the problem and you want to restore them. The preferences file is usually in the Preferences folder in the System Folder, but it could be somewhere else, such as in the folder with the program (or in the "Claris" or "Aldus" or "your software brand name here" ...