No problems. Visual Studio is still mainly aimed at 32 bit platforms on the C++ side. I use Vista x64 to develop apps for Windows Embedded Standard (basically XP Pro), and there are no real problems. You do, however, need to understand that Winx64 behaves differently than x86. When you run a 32 bit app in x64, it's run in a 32 bit "copy" of windows really. It's mainly the registry that you need to look out for (and all that depends on the registry such as ODBC, etc). Windows put keys and values from 32 bit apps in subnodes called "Wow6432Node". For instance, if you read/write from HKLM\Software\YourKey, Windows will redirect your keys to HKLM\Software\Wow6432Node\YourKey. Other than that, I haven't found any issues.