I just enrolled in Insider Program yesterday in Slow configuration and got Build 10166 just to found out that the build I had is already outdated. I had it successfully installed on my phone. Soooo many bugs and errors that it freaks me out. So I reinstalled Windows Insider and enrolled now in Fast configuration. I checked for update and notified me that build 10581 is available for my device. Is it okay that I enrolled again in Insider program in which I already have had enrolled yesterday in slow? I am now running Windows 10 Preview build 10166 and currently downloading build 10581.