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For a few bucks you can get a Serial to USB adapter, which will install a virtual COM Port to operate the hardware. You can also find software to create virtual com port pairs connected by a virtual null-modem, so two copies of KSTerm running together can let you send and receive between them. The Open-Source version I use is com0com - http://com0com.sourceforge.net/.
For about the same price as a USB-Serial dongle you can get a micro-controller board with built in TTY that provides a virtual Com Port, and lets you be creative with what you can build!
I have no affiliation with them but I'm a big fan of the TeensyUSB from:
https://www.pjrc.com/
KSTerm was mostly developed for use with several projects using TeensyUSB boards, which have built-in UARTs (notice the plural), and provide a Virtual COM Port as part of the board programming interface.
They are also Arduino compatible - but they leave Arduinos in their dust for speed and have many very useful support libraries and examples.
KSTerm has been used successfully in various forms on Windows 10, 7 and XP
(in theory all should work fine on Vista and 8, but someone would have to use them to know.)