E-SWORD is a great, free, Bible study program, with a powerful search utility, and customizable resources, including all the old stand bys, like Matthew Henry's, Barnes complete notes, Gills, Halleys, and many many more...
It allows comparitive studies between versions which is useful whether you are King James ONLY (which I am) or not...It also has the Textus Receptus (in Greek) as well as the Hebrew OT. The King James is availabe as is, or in the 1611, or with Strong's numbers that open when you hover on them. Some of the resources come at a reasonable cost (like the NIV), but most are FREE. Free has always been one of my favorite words, and now for a whole new reason.
http://www.e-sword.net/