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You have to provide far more information. I know nothing about your CNC control, I have no idea what a y2k pc is, and what is your definition of DNC?
My definition of DNC is Direct Numerical Control (drip feed).
2400 baud is a very low baud rate, but that should not be the origin of your problem. This baud rate just takes along time to transfer data.
What kind of format does your CNC require for the file structure? HAAS and Fanuc use this structure
Can you send a program from the CNC to your computer? This is probably the place to start.
What handshake mode are you using?
Is your computer running Windows and what version?
Have you previously used a different computer and been able to communicate?
These are just a few possible questions.