Quite some time ago, I developed a Win32 console app to program the AT89S8252 by "bit-banging" SPI over a standard PC serial port. RS-232 signal level shifting was performed in the target hardware. I believe that the AT89S52 uses the same programming means as the 'S8252, but I only skimmed the 'S52 datasheet. If the source code for this application would be of any benefit to you, e-mail me a request for an unsupported copy of this MS Visual C++ source code (100% C though).