I updated to the latest version after seeing a message in BOINC. I downloaded and installed Windows 7 x64 and now have both 32 and 64 bit running. How do I get rid of the 32 bit? Can I remove everything and reinstall x64 without losing my existing tasks and preferences?

Please uninstall BOINC through Control Panel->Uninstall a program.
That will delete the program files only.

It's probably uninstalled the 64bit version now, from C:\Program Files\BOINC\ and left the 32bit version in C:\Program Files (x86)\BOINC\ intact. So delete this directory. Then reinstall the 64bit BOINC. This will reinstall itself in C:\Program Files\BOINC\

That the program directories changed is a Windows thing. By default, Windows 7 and Vista will try to install 32bit programs to the \Program Files (x86)\ directory and 64bit programs to the \Program Files\ directory. 64bit programs cannot be installed in and run from the 32bit directory, but I think 32bit programs can be installed in and run from the 64bit programs directory. Windows security, etc.

Normally when the BOINC installers starts, it'll read from the registry where the BOINC programs directory is housed and it will try delete the old program files from the programs directory and try to install the new BOINC program files to that same directory. It's very well possible that the 64bit installer does not have permission to delete files from a 32bit directory, or that, since it's a 64bit installer, it will forgo the check in the registry and install to the 64bit directory automatically, without deleting the old program files. I'll ask the developer when I next talk to him.

It's not possible to run BOINC twice, although it is possible to run BOINC Manager twice. You're probably seeing that.

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