If we can verify it's a genuine Teensy++ 1.0 made by PJRC and we can look up the original purchase info, PJRC will replace it at no charge with either Teensy++ 2.0 or Teensy 3.2 (your choice).
If you really want to program it anyway, you can still use WinAVR with a makefile and the old USB code to produce the HEX file. Teensy Loader still supports Teensy 1.0 and Teensy++ 1.0. But Teensyduino does not. Arduino/Teensyduino support for those very old boards was dropped years ago. In the early days when those boards shipped, the Arduino support at the time was very primitive... pretty much everyone used WinAVR & makefiles back then with those 1.0 boards. The Arduino support was never well tested and mature and used by many people on those boards, so it made a lot of sense to just drop it.