Cannot connect with Win PC via Screen Sharing

[MrMister111]

I used to be able to connect to my Win XP PC from my iMac, both wired in same house, but now I get the error message

The software on the remote computer appears to be incompatible with this version of Screen Sharing.

What does this exactly mean please, I can connect via my iPhone VNC fine, the same IP is in etc. I can ping the address from my Mac to the Win PC so it can "see" it

It used to work, maybe on ML before, I now have Mavericks 10.9.4.
Thanks

 

[MrMister111]

tried everything I know in my limited ability. Anyone know more about this and connect to a Win PC XP from an iMac please

thanks