So it looks like I am one of the MANY people unable to upgrade to 4.0. I am now $40 poorer and totally unable to use PC applications on my Mac. To top things off, the Parallels support team has gone quiet instead of OPENLY addressing on their website the fact that there is a MAJOR problem. They should also pull the upgrade from the website until the issues are resolved. DID THE PARALLELS QA TEAM TEST THIS PRODUCT BEFORE IT WAS RELEASED?? From the number of posts about the 4.0 upgrade disaster, it looks like the answer is NO. Like many other people, I have the issue that during the upgrade from 3.0 to 4.0 on my Mac (v. 10.5.5.) the process quits in Step 1 of 4 while upgrading the image (XP). Before it quits to show a logo, I get a Windows black screen for a fraction of a second. That screen states in part "Windows did not start successfully. A recent hardware or software change might have caused this". I only know it states that because I took a screen capture during that split second. Although I see many users have had this exact issue, it looks from the posts that other users have had the process fail elsewhere. In any case the number of posts in the forum regarding issues with upgrading to 4.0 is numbing. Parallels has totally mishandled not only the upgrade, but its response to the disaster. I publicly request an acknowledgement on the Parallels site, so that other users thinking of upgrading are aware that their capability to run Parallels on a Mac has a significant chance of being put on hold indefinitely. Parallels team; please either acknowledge the issues or pull the plug on 4.0 until those issues are resolved, the current situation is not right. Don't expect your users to do the testing of new products for you.