oh, from what I can gather, the error is caused by one of several possible problems.
Install the .NET fromework 1.1- see if that fixed it?
Corrupt installation or file. Need to manually delete the files off the machine and then reinstall and have it uninstall it.
make sure you have enought freespace on your machine. i.e >1 gb
The NIS error is from this...
Nullsoft Scriptable Install System - http://nsis.sourceforge.net/
Read up on it if you need more infor and there are forums there that will provide details to the problem. To much info for me to go through...
if you don't get the program to uninstall, then look here for manual removel instructions.