I bought to prepare Kaplan GMAT Premier Program 2007 Barron's GMAT 16th Edition. After 4 weeks, practicing with two books I have to say that Kaplan's statements are too complicated. In addition, the CD with the test does not work, which is very annoying; mainly because Kaplan offers no solution. In Kaplan's support page you can then read the small print that the software is designed only to Windows XP. Windows Vista and 7 are not compatible. The CD can not call in compatibility mode. With Barrons I am, however, very satisfied.