Just had the same problem installing in XP. Found the fix below in 1 of the threads - worked for me:

[1] Open your browser to the following URL. You may need to do this through MSIE (ugh). I tried downloading this file (probably from a different location) via LimeWire.com's website FAQ and the file was corrupted and refused to install. The URL below is correct. Manually download and install it or, using MSIE, select 'open' during download instead of 'save'.

http://www.installengine.com/isengine/isscript.msi

Good luck