My experience, based on selling and shipping about a dozen systems on the FS/FT forum via USPS, is that the key thing is how well the system is boxed and protected. The best boxes I used are from Dell; after all they ship millions a year. However, any strong box with good foam, or better yet, double boxed with foam, will do. I never had a problem with any hard drive not working. The thing you need to be most careful about is removing any really heavy heat sink that's only clipped on--the torque can pull them loose. And, of course, buy insurance.