You need at least Microsoft Visual C++ 2008 Express.
Also make sure you have installed OpenSSL 32bit version, the full installer. Not the light.
Here's the links for the programs:
http://go.microsoft.com/?linkid=7729279
Shining Light Productions - Win32 OpenSSL
If you don't already have this .Net Framework 3.5, I suggest you getting it.
Download Microsoft .NET Framework 3.5 from Official Microsoft Download Center
Announcements: I will be providing some information about the source and the above error in the FAQ soon.
I'll be uploading v5.0.6 very soon, I'm just compiling once again for TrinityCore's latest commit.