Hello Koasmimi,
They are two D/L
The 64-bit version is for 64-bit OS versions. Is named Windows Defender64.msi
The 32-bit version is for the 99% of the users is named Windows Defender.msi
<The installation package is not supported by this processor type.>
The message appears to also be caused by a corrupted or incomplete download.
I'd recommend re-downloading, and saving to a known location--like the
desktop.
After the download is complete, disable real-time protection by your
antivirus for long enough to do the installation.
ANONYMOUS put you in the right track.
Good luck