I saw a post somewhere on this board that stated it took 5 minutes for Parallels 4.0 to load. So I exited to the program to time my boot time and the result was 59 seconds from the time I clicked start until I could open a program. My previous 3.0 probably took 3 or 4 minutes and was very sluggish. Strangely enough, I down graded my Parallels memory to 1 GB. I was using 2 GB with 3.0 on the same computer (MacBook).
