Packet Data - how to setup PC connected to tetra radio

[uy0101]

Hi,
i'm trying to setup packet data connection on Windows OS (WIN7, WIN8) but without success.
i always get errors stating that windows cannot communicate with the modem.
I've checked modem logs and i see actual responses form radios (PEI interface) but in the end conenction is not established.

I'm using ******** MTM800 with RS232 cable connected from rear radio connected to COM1 on PC
Does anybody has a guideline about PC setup for PD?
Regards
uy