use ATMEL FLIP
What you have is a 40 pin 8051 device with 64K flash memory, with dual data pointers and an ISP programming interface. (lots of other stuff too)
They are good devices! I use them all the time. The best thing is that the ISP programming interface uses the uart pins already wired to a Max 232 circuit on most boards.
To program it you can use flip from atmel. This program works well in windows and also can be run by command line (batch files with cmd files)
Do a search for FLIP (Flexible In System Programmer) on the atmel website.
If you can't find the datasheet for that particular device, let me know I have it.
You can also get the Temic T89C51RD2 datasheet which is very similar (not 100%, but the pinout is exactly the same)