PGP is an encryption method. It stands for "pretty good privacy". It is debatable as to whether it can be broken. Contrary to popular myth, there is no "back door" to PGP. It is conceivable it could be broken but the time and effort required would be enormous. Not likely for an individual or small time distributor.
For those that want to encrypt their entire hard drive, PGP has an excellent product out that will do that. It is reasonably priced for this type of technology and without a passphrase nobody will be able to access the info on your harddrive. You can get it at:
www.pgp.com
Keep in mind, your passphrase is what will determine the security of your hard drive. I suggest a very long, nonsensical passphrase along the lines of the following:
liueRTcnm2290765lrAWDCGUjinepp8276318MN74zkBIENUme icw9G
Since nobody can remember such a passphrase, you'll have to write it down and keep it well hidden. One way is to randomly highlight letters and numbers out of a book. They you'll use all highlights from page 46-77. Only you will know what pages to use and with every page in a 200 page book with highlights, it would be basically impossible for someone to break your code. If you do this, highlight the same number of characters on every page so you don't give anything away that way.
Is this a hassle to do and input everytime you sign on to your computer, yes. Is it virtually unbreakable? Yes. Your choice. Be aware that a random group of words isn't a good choice for a passphrase. There are brute force dictionary based software programs that can break them.
Good luck,
MaxRep