Apple has begun a MacBook Repair Extension Program for Hard Drive Issues to repair or refund owners of black or white MacBooks sold between approximately May 2006 and December 2007 who have suffered faulty hard drive issues.
Symptoms are described as a flashing question mark on the screen at which point Apple will "examine the hard drive to confirm if it is eligible for a replacement, free of charge, under this program."
More specifically the issue that seems to effect MacBooks with Seagate hard drives is said to only prevail on 13-inch MacBooks with a processor speed of 1.83GHz, 2GHz, or 2.16GHz and one of the following hard drive capacities 60GB, 80GB, 100GB, 120GB, or 160GB.