What variant of the ST7 are you trying to program, the early types used ISP - the latter use ICC.
Using a parallel port is very easy with the ICC variants, slightly harder with the ISP variants
You can try with the Freeware version of CodeVision AVR.
The web page: https://www.hpinfotech.ro/
I do not know if you can download it from there..., so try.
Then you can programm the unit with a home made parallel port programmer, using In System Programmer for Atmel.