Why can't I install this?

I have a pc with Windows 7 Pro x64.
Over the weekend I did a clean install onto a new Samsung hard drive. The install went well with no problems that I know of.
Prior to making my first image I tried to install Code Dawn's Quickmonth Calendar. I've been using it on other pc's without a problem. I used it with this same OS on the old hard rive. It worked as it was supposed too.
But his time, it refuses to start. Even if I go to All Programs and Startup and try to start it from there, it will not open up.
All I get is the spinner for a few seconds and that's it.
I know that glitches like this do pop up sometimes.
But I don't know why or how to get around it.
All security software was off at the time. Actually, most of it had not yet been installed.
Any help would be great.
Thanks.
H

Did you install it as administrator? Right click program > run as administrator.

Login as administrator to install new software

Limited help on the website. Try uninstall and re-install, but run the install as admin.

The website say "improved" compatibility.

I just installed using Run as Admin. Turned off recently installed MSE v2 and Prevx. Windows Defender is off and UAC is set to never notify for now.
Then tried to start it as Admin.
Same problem. I see the spinner for about a second then nothing.
I had it working with no trouble on a prior install of this same OS from the same disc from MS.
I think I need to find another unobtrusive free calendar and try that.
Thanks.
H.

PS: Also tried using MS's Compatibility troubleshooter. Nothing seems to work on this problem.

Check your Event Viewer to see if there is a clue.

I love RainLendar.

Went to event viewer and spent some time between it and MS help site.
Nothing even remotely related to my problem.
My system comes out being healthy.
The one underlying theme I've run into is that W7 x64 seems to be 'quirky'. Whatever that means. I understand the word, I just have trouble with software being quirky.
Thanks all for your help.