BizTalk itself can be installed and configured in about an hour if everything goes well.
If you are starting from scatch however, you should probably allow at least one full work day. By this, I mean you build a Virtual PC or a new machine and install all the prerequisites.
Here is a list of things I installed on a new Virtual PC, in preparation for creating a new WCF/BizTalk course:
Windows 2003 – about 1.5 hours
Windows 2003 SP2 – about an hour
SQL 2005 – about an hour
SQL 2005 SP3 – about an hour
Visual Studio 2005 – about an hour
Visual Studio 2005 SP1 – about an hour
Visual Studio 2008 – about an hour
Visual Studio 2008 SP1 – about 1.5 hours
Create userids and groups before BizTalk Install – about 10 minutes
BizTalk 2006 R2 – about an hour
It all adds up fast. All the above take about 10 hours, but you can be doing other things while all the installs are running.
I did the above on a 500 GB USB drive, so it might actually run faster on a real machine, local disk, non-virtual.
I did not include SharePoint or MOSS on the above install. The time above also excludes the time to install Office (Excel and Infopath – needed for BAM and Trading Partner Management).