Users are most concerned about Windows 7's migration and application compatibility issues, according to a sweeping survey of online forums, Web sites and social networking services, a support firm said today.iYogi, a New York-based tech support company pushing Windows 7 upgrade services, said that it tracked tens of thousands of online conversations during the past week about Windows 7 to come up with the top 10 user worries about Microsoft's new operating system.The company monitored 10 major forums, including MSDN, TechNet, Yahoo Answers and Google Groups; 25 sites posting user reviews, such as Amazon.com , CNET and Epinions.com ; and social sources including Facebook and the micro-blogging service Twitter.At the top of the iYogi list was concern about Windows 7's application compatibility and migration from earlier editions to the new OS. One sample question iYogi logged: "Do I need to re-install Microsoft Office when I upgrade to Windows 7?" (Answer: Yes, if upgrading from Windows XP.)Microsoft has directly addressed compatibility concerns with the Windows 7 Compatibility Center , a site that launched yesterday, which lets users root through a massive database of hardware and software to find which peripherals and programs are up to snuff.On the upgrade front, Microsoft has posted a several-step tutorial to guide Windows XP users through the process. (For more on upgrading from XP, see Computerworld 's "FAQ: How to prep for an XP-to-Windows 7 upgrade." )Second on iYogi's list were worries about Windows 7's new features -- how different the new OS is from the familiar XP -- while in third place were questions about its performance. "Is Windows 7 faster than XP or Vista?" asked one user, said iYogi. ( Computerworld 's Windows 7 expect, Preston Gralla, says yes.)Other concerns ranged from getting ready for Windows 7 (No. 4) and the operating system's user interface (No. 5) to how much time it will take to install Windows 7 (No. 8) and whether its price will ever drop (No. 9).Not surprisingly, iYogi also touted polls it conducted that claim nearly 70% of Windows users aren't "entirely comfortable" that they would be able to move their favorite applications to Windows 7.Microsoft has built a Windows 7 help and support site that includes how-to videos, links to company-sponsored user-to-user forums, and answers to what it considers the top user-submitted questions.Microsoft will host a New York City launch event tomorrow at 11 a.m. ET, when CEO Steve Ballmer will kick off a coming-out party.