Here is what I did:
Downloaded the file php_rrdtool.tgz   (Dated 04-Dec-2005 23:24 9.1K ) from http://oss.oetiker.ch/rrdtool/pub/contrib/

Compiled it with VC 6 (had to build a project file).

If you use this let me know if it works.

I do use rrdtools.exe with mrtg to graph the vitals of most servers I manage. It's a great tool!