For Win32 you don't need to compile GD, the module's binary is precompiled in the zip distribution downloadable off php.net. Simply:
1) grab that archive
2) extract it to your php folder (c:\php4 for the sake of this example)
3) edit the extension_dir directive in php.ini to the following:
extension_dir = "c:/php4/extensions/"
make sure you use the Unix forward slash and have a trailing slash on the path
4) add or uncomment "extension=php_gd.dll" (also in php.ini)
5) restart Apache
GD should now be happily running on your server. HTH.
geoff