Release 300
This is the first release to support only Python 3.5 and up - Python 2 is no longer supported. To celebrate, the build numbers have jumped to 300! There were significant changes in this release - you are encouraged to read CHANGES.txt carefully.
To download pywin32 binaries you must choose both the correct Python version and "bittedness".
Note that there is one download package for each supported version of Python - please check what version of Python you have installed and download the corresponding package.
Some packages have a 32bit and a 64bit version available - you must download the one which corresponds to the Python you have installed. Even if you have a 64bit computer, if you installed a 32bit version of Python you must install the 32bit version of pywin32.
To determine what version of Python you have, just start Python and look at the first line of the banner. A 32bit build will look something like
Python 3.8.1+ ... [MSC v.1913 32 bit (Intel)] on win32
While a 64bit build will look something like:
Python 3.8.1+ ... [MSC v.1913 64 bit (AMD64)] on win32
If the installation process informs you that Python is not found in the registry, it almost certainly means you have downloaded the wrong version - either for the wrong version of Python, or the wrong "bittedness".