Unregister a XLL in Excel (VBA)

I am just discovering the world of programming XLLs for Excel using XLW under Visual C++ 2010 and everything has been smooth so far using the template provided with the XLW package, I have a few questions:

1. I found out that I can register an XLL by double-clicking it. What other ways are there, especially from VBA or the Excel menu?
2. How can I unregister an XLL, both via the Excel GUI and VBA? I assume this has to be done each time I rebuild the Xll under Visual Studio.
3. Does Excel 2010 64-bit require XLLs compiled and linked for 64-bit?

Thanks, Steve