Check where your downloads go.
Downloading to the desktop is definitely NOT a good location. The desktop should ONLY contain shortcuts to some often used applications and documents.
It's much beter to set a dedicated download folder.
So, follow those steps:
Create a downloads folder and set it as your default download location.
Click the "Download now" button or link.
Open your downloads folder. (you can put a shortcut to it on your desktop)
Find the downloaded file. Setting the view to "Details" and sorting on the date can help.
Doubleclick the installer.
Follow the instructions. Sellect "Custom" installation.
DECLINE any and all offers and so called "recomended" changes/download/side installs. Those are absolutely NOT needed.