The primary sign that you are having a hard-drive issue on your MacBook is the flashing question mark when starting up. Should your machine fall into the eligible model range, you will be given a replacement drive, free of charge.
Apple has a knowledge base article relating to the program:
Affected MacBook modelsDid you already pay for an out-of-warranty repair? Don't worry, Apple is thinking of you too:
13-inch black and white MacBook models with the following processor speeds and hard-drive capacities:
- Processor speed - 1.83GHz, 2GHz, or 2.16GHz
- Hard drive capacity - 60GB, 80GB, 100GB, 120GB, or 160GB
"Some customers may have paid for out-of-warranty repairs that qualify under this program. Apple will contact affected customers (where contact information is available) with details on the reimbursement process. If you believe that you paid for a repair covered by this program and you have not been contacted, you may contact Apple Technical Support.
This worldwide Apple program does not extend the standard warranty coverage of the MacBook.
This program covers affected MacBook models for 3 years from their original date of purchase or until August 15, 2010, whichever provides longer coverage. Apple will continue to evaluate the repair data and will provide further repair extensions if needed."