I am currently developing using 4.8.4 SOURCE. My SOLUTION (22 projects) build time is 2-7 seconds. And this is in a VMware virtual machine using windows server 2003. The host machine is running XPpro with Intel Core 2 Duo T7500 @ 2.2GHz and 4GB RAM.
So 20 MINUTES (1200 Seconds) is extraordinary.
Something is really wrong with your setup to take 20 minutes. When watching the build output as it's compiling, what modules are taking the longest? Sit down with a stopwatch and a notepad and take some notes.
FYI, here is what my build output of the CORE looks like:
------ Build started: Project: CountryListBox, Configuration: Debug Any CPU ------
CountryListBox -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Library\Controls\CountryListBox\bin\CountryListBox.dll
------ Build started: Project: DotNetNuke.Syndication, Configuration: Debug Any CPU ------
DotNetNuke.Syndication -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Library\Components\Syndication\bin\DotNetNuke.Services.Syndication.dll
------ Build started: Project: DotNetNuke.WebUtility, Configuration: Debug Any CPU ------
DotNetNuke.WebUtility -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Library\Controls\DotNetNuke.WebUtility\bin\DotNetNuke.WebUtility.dll
------ Build started: Project: DotNetNuke.Library, Configuration: Debug Any CPU ------
DotNetNuke.Library -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Library\bin\DotNetNuke.dll
------ Build started: Project: Provider.Membership.DataProvider, Configuration: Debug Any CPU ------
Provider.Membership.DataProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Membership.Dataprovider.dll
------ Build started: Project: Provider.SqlDataProvider, Configuration: Debug Any CPU ------
Provider.SqlDataProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.SqlDataProvider.dll
------ Build started: Project: DotNetNuke.HttpModules, Configuration: Debug Any CPU ------
DotNetNuke.HttpModules -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.HttpModules.dll
------ Build started: Project: Provider.Membership.DNNProvider, Configuration: Debug Any CPU ------
Provider.Membership.DNNProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Provider.DNNProvider.dll
------ Build started: Project: Provider.Membership.AspNetProvider, Configuration: Debug Any CPU ------
Provider.Membership.AspNetProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Provider.AspNetProvider.dll
------ Build started: Project: Provider.Search.DataStore, Configuration: Debug Any CPU ------
Provider.Search.DataStore -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Search.DataStore.dll
------ Build started: Project: Provider.Search.Index, Configuration: Debug Any CPU ------
Provider.Search.Index -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Search.Index.dll
------ Build started: Project: Provider.DNNScheduler, Configuration: Debug Any CPU ------
Provider.DNNScheduler -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.DNNScheduler.dll
------ Build started: Project: Provider.SolpartMenuNavigationProvider, Configuration: Debug Any CPU ------
Provider.SolpartMenuNavigationProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.SolpartMenuNavigationProvider.dll
------ Build started: Project: Provider.DNNTreeNavigationProvider, Configuration: Debug Any CPU ------
Provider.DNNTreeNavigationProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.DNNTreeNavigationProvider.dll
------ Build started: Project: Provider.DNNMenuNavigationProvider, Configuration: Debug Any CPU ------
Provider.DNNMenuNavigationProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.DNNMenuNavigationProvider.dll
------ Build started: Project: Provider.DNNDropDownNavigationProvider, Configuration: Debug Any CPU ------
Provider.DNNDropDownNavigationProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.DNNDropDownNavigationProvider.dll
------ Build started: Project: Provider.XMLLoggingProvider, Configuration: Debug Any CPU ------
Provider.XMLLoggingProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.XMLLoggingProvider.dll
------ Build started: Project: Provider.DBLoggingProvider, Configuration: Debug Any CPU ------
Provider.DBLoggingProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Provider.DBLoggingProvider.dll
------ Build started: Project: Provider.Caching.FileBasedCachingProvider, Configuration: Debug Any CPU ------
Provider.Caching.FileBasedCachingProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Caching.FileBasedCachingProvider.dll
------ Build started: Project: Provider.Caching.BroadcastPollingCachingProvider, Configuration: Debug Any CPU ------
Provider.Caching.BroadcastPollingCachingProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.Caching.BroadcastPollingCachingProvider.dll
------ Build started: Project: Provider.ASP2MenuNavigationProvider, Configuration: Debug Any CPU ------
Provider.ASP2MenuNavigationProvider -> C:\Inetpub\wwwroot\DotNetNuke.4.08.04\Website\bin\DotNetNuke.ASP2MenuNavigationProvider.dll
------ Skipped Build: Project: http://localhost/DotNetNuke_4.8.4/, Configuration: Debug .NET ------
Project not selected to build for this solution configuration
========== Build: 21 succeeded or up-to-date, 0 failed, 1 skipped ==========