Why do I get NSIS Error?

A NSIS Error message box means the installer you're trying to run is corrupted. It means the installer data was somehow modified and is no longer valid. The error states:

The installer you are trying to use is corrupted or incomplete.
This could be the result of a damaged disk, a failed download or a virus.

You may want to contact the author of this installer to obtain a new copy.

It may be possible to skip this check using the /NCRC command line switch
(NOT RECOMMENDED).

Solutions

Follow these steps for each case to get rid of the error.

Error with Single Installer

1. Disable any download accelerators and download the installer again.
2. Update any active anti-virus and download the installer again.
3. Disable any active anti-virus and download the installer again.
4. Download the installer from another source. It might be corrupted on the server, or the connection to the server is unreliable.
5. Download the installer using another computer and copy it to the original computer using a reliable medium.
6. Rename the installer so it is a simple one-word name with no special characters (without removing the .exe suffix)

Random or Start-up Errors

1. Scan for, and remove malware

Error When Closing Internet Explorer

1. Try updating McAfee manually. Failed updates of McAfee have been known to produce this problem.
2. Scan for, and remove malware