When I try to compile php under Winnt with visual C++ 5.0, I have this error :

basic_functions.c
.\functions/md5.h(65) : error C2061: syntax error : identifier 'UINT4'

This is because file global.h has been modified from version 3.0.7 : 

/* UINT4 defines a four byte word */
typedef unsigned long int UINT4;

has become:

/* UINT4 defines a four byte word */
#if SIZEOF_INT == 4
typedef unsigned int UINT4;
#elif SIZEOF_LONG == 4
typedef unsigned long UINT4;
#endif

But you don't have any definition of SIZEOF_LONG in the config.win32.h file. (running ./configure set its value to 4 under a good old UNIX system...:)