The suggestion provided below to remove unwanted games may be unexpected, but there's a reason for it: If your game installation is incomplete (or you've uninstalled the game from your computer's control panel instead of the Download Games Manager), the portion of the program responsible for uninstalling may be missing and you probably are receiving an error message like "Uninstallation failed"
To ensure a full uninstall/removal, it’s best to have the complete full version of the program.
You'll need to download the game again onto your computer to uninstall it. The error message you are getting is because the portion of the program that handles the uninstallation has been removed. Once you reinstall the trial version of the game, you'll be able to remove it normally.
Step 1: Reinstallation:
You can install the game on your computer by downloading the "Play Free/Play Now/Download Now" demo and saving the game's installer to your computer.
The Download Games Manager should open giving you the time remaining status for your game to complete download.
When the download finishes, you will receive a prompt to "Play Later" or "Play Now." Select "Play Later."
Step 2: Uninstalling.
To uninstall a game from the Download Games Manager: All you need to do is simply click the red "X" button next to the game's listing from the "My Games" section of the Download Games Manager.
1. Click "Start."
2. Go to "My Computer."
3. Go to C drive (or the letter designation for the drive name your games are stored on)
4. Open the "Program Files" folder
5. Locate the iWin.com folder and open it.
6. Locate the game file you wish to remove.
7. Right click on it and delete.