The ETS website has a downloadable program to help you with that: PowerPrep II. However it only has two practice tests.
New! POWERPREP® II, Version 2.0 Software: Preparation for the computer-based GRE revised General Test
In addition to the sample questions, strategies and tips available here on this site, this free software also includes two full-length practice tests. ***These timed tests simulate the test taking experience, including the test-taker friendly design features like moving back and forth and changing answers within a section, as well as the on-screen calculator.***
Learn more about POWERPREP II, Version 2.0 Software >
Found here: GRE Revised General Test: POWERPREP II Software
PrincetonReview also has one free practice test on its website: Free GRE Online Practice Test
I totally agree it's annoying to shift from paper to computer. I hope these links help! There's also the possibility that any study books you bought have a CD with practice tests on it, too.