Thanks for the screenshots. This makes it a lot more clearer what the problem might be.
(PS: in the future when you have other problems, always state the exact and complete error message you got. Don't describe it, but state the text exactly (and/or take a screenshot), including all the detailed steps you took. In that way people can help you directly and much quicker and don't need to guess 
)
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First thing to do and check:
Did you uninstalled Messenger Plus! Live and its sponsor in the proper way? In other words: when you uninstalled it, did you saw a box comming up with big numbers and did you filled out those numbers when they were requested?
If so, you probably uninstalled Messenger Plus! Live and its sponsor correctly. If you didn't saw such a box, you probably failed to uninstall the sponsor of Messenger Plus! in the proper way. To solve this you need to install Messenger Plus! again WITH the sponsor. When that is done, you can uninstall everything again, but this time follow the instructions on the screen carefully.
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Second thing to do and check:
1) Uninstall EVERY addon or extra tool for Messenger. This includes stuff like SmileyCentral, SweetIM, etc... You must uninstall these by going to you "add/remove programs" control panel.
Also see and read
Have SweetIM and/or SmileyCentral installed? PLEASE READ.
2) Uninstall ALL Messenger clients you may have installed (with the use of the 'add/remove programs' control panel - Never ever just remove/delete programs).
3) After uninstalling everything, make sure to delete "C:\Program Files\MSN Messenger" and/or C:\Program Files\Windows Live\Messenger". This is very important.
4) The error: "This application has failed to start because MSNcore.dll was not found." can have several other causes. The official support from Microsoft states the following:
quote:
To resolve this issue, we are going to check hard disk space, decrypt Temp folder and reregister Windows Installer files. I have research the steps for you below and please follow them as listed. I appreciate your patience on this.
[list=1][*]Exit Windows Live Messenger completely. This means right click on its icon in your systemtray and choose "exit".
[*]Verify that you have sufficient disk space on your hard disk:
- Right-click the "Start" button, and then click "Explore."
- In the "Start Menu" window, right-click drive C in the left window, and then click "Properties."
- Make sure that you have at least 50 megabytes of free space on drive C. If this is not the case you need to free up some diskspace first by removing other programs and/or files and/or cleaning out your trashbin, and/or cleaning your temporary files folder.
[*]Use the Disk Cleanup Manager utility to clear the temporary files and folders:
- Click "Start," click "Run," type "cleanmgr", and then click "OK."
Note: If you have more than one hard disk in your computer, the "Select Drive" window appears. If this is the case, select drive C on the drop-down menu, and then click "OK." The Disk Cleanup utility analyzes the drive to determine the amount of free space that you can achieve.
Note: This process may take several minutes.
- In the "Disk Cleanup for C:" window, click the "Disk Cleanup" tab.
- Click the check boxes to select the following items:
- Downloaded Program Files
- Temporary Internet Files
- Temporary Files
- Temporary Offline Files
- Offline Files
- Click "OK" to delete the selected file types.
- When you are prompted, click "Yes" to start the Disk Cleanup utility.
Note: This process may take several minutes.
[*]If your computer is running Microsoft Windows XP or Microsoft Windows 2000, the Encrypting File System may have encrypted the %temp% folder on your computer. If the Encrypting File System encrypted this folder, you must temporarily decrypt the folder before you install Messenger. To do this, follow these steps:
- Click "Start," click "Run," type "%temp%\..\", and then click "OK."
- Right-click the Temp folder, and then click "Properties."
- In the "Temp Properties" window, click the "General" tab, and then click the "Advanced" button.
- In the "Advanced Attributes" window, under the "Compress and Encrypt attributes" section, click to clear the "Encrypt contents to secure data" option.
- Click "OK" two times to save the changes and to close the "Temp Properties" window.
[*]If you have a spyware detection tool running on your computer when you try to install Windows Live Messenger, you must disable it.
[*]If you had an earlier version of Messenger installed, uninstall it via the "add/remove programs" control panel.
[*]Try to install Windows Live Messenger again. For more information, go to step 11.
[*]If you still receive the error message, spyware may be preventing Windows Live Messenger from installing correctly. Some spyware can affect the system files that your system requires to connect to the Internet. To remove the spyware use an anti-spyware or an anti-virus tool. Restart your computer afterwards before continuing.
[*]If you still receive the error message, re-register Microsoft Windows Installer files:
- Click "Start," click "Run," type "msiexec /unregserver", and then click "OK."
- Click "Start," click "Run," type "msiexec /regserver", and then click "OK.
[*]If you still receive the error message, re-install Microsoft Windows Installer files:
[*]Try to re-download and re-install Windows Live Messenger again. To do this:
[/list]
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