How about Tags, So if a user creates a topic, he can add tags and if someone clicks one of the tags, all topics with similar or identical tags show up. Or a user can go to a page with a list of all tags being used and click on one and he will be shown all topics with the same tag.
For example, if you are trying to find all threads about motherboard problems, you simply click the tag and are shown topics with the same tag- Motherboard problems, the rather than every mention of a motherboard problem in a completely irrelavent post and topic.
No, it wouldn't do much to existing topics but it would certainly have an impact on future topics.