Unable to open the game. Main exe says you need to use a manager program to launch the game. The exe called "HardMan" only has an option for installing, and that fails.

The installer writes registry keys which Hardman.exe checks for to see what to do. Because the download doesn't come with any reg keys it tries to patch the game but the files aren't there as it's already pre-patched.
Here's the keys that are missing:
("C:\path\to\gamedir" will be something like "C:\Games\Hardwar")

[Software\Refinery\hardman\Config]

"DataPath"="C:\path\to\gamedir\DATA"
"DataPath2"="C:\path\to\gamedir\DATA"
"GDVPath"="C:\path\to\gamedir\GDV"
"GDVPath2"="C:\path\to\gamedir\GDV"
"GDVPath3"="C:\path\to\gamedir\GDV"
"installed"="V2"
"RunPath"="C:\path\to\gamedir"
"SavePath"="C:\path\to\gamedir\Savegames"
"Skin0"="C:\path\to\gamedir\moth_moon.bmp"
"Skin1"="C:\path\to\gamedir\moth_silver.bmp"
"Skin2"="C:\path\to\gamedir\moth_neo.bmp"
"Skin3"="C:\path\to\gamedir\moth_hawk.bmp"
"Skin4"="C:\path\to\gamedir\moth_death.bmp"
"Skin5"="C:\path\to\gamedir\moth_police.bmp"
"Skin6"="C:\path\to\gamedir\moth_swallow.bmp"
"SkinDir"="C:\path\to\gamedir\"
"SourcePath"="C:\path\to\gamedir"
"version"="UIM.06"

That's it. Run regedit, navigate to Software/refinery/... etc and enter all these key value pairs. Don't know if it's case sensitive so assume that it is. On Windows you might need to restart after changing registry. Probably not for this, but it's a possibility.
Good luck.

EDIT: The path name might need double backslashes (\) instead of single ones. Not sure as I'm running this on Linux

Try re-download at abandonware