[Ivan Kim Reyes]

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Insider Program yesterday in Slow configuration and got Build 10166 just to found out that the build I had is already outdated.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.

[PepperdotNet]

Yes of course it's ok. That is exactly how Insider works.

You "enrolled" once, when you signed up at the Insider.Microsoft.com website. What you are describing is simply choosing which set of builds you want to install.