The best thing to do then is to uninstall php from the Add Remove programs and remove IIS. Then restart the PC and perform the reverse (install IIS and then PHP) Ensure that these two work perfectly and then grab the gdlib library for windows. Perhaps the copy of the gdlib is from a previous version or just a different distro.
www.experts-exchange.com has some really good advice on those issues.
Sorry that I cannot be of any more help...
