X1 Search does not support XP. X1 Search 8 supports Windows 7, and Windows 8.
X1 Search was not designed or intended for use with Windows XP, as Microsoft has stopped support for XP: http://windows.microsoft.com/en-us/eos.
While some users have been able to run X1 Search successfully in an XP environment previously, unfortunately, some of the changes we've made to our most recent builds (versions 8.3 and higher) have made installing current builds of X1 Search on XP impossible.
We regret any inconvenience.