After upgrading my work laptop to Vista Business to begin testing Vista I noticed that my CPU usage was really high and it was becuase of searchfilterhost.exe using about 50% of my CPU resources.
I found an easy solution, removing .xml files from the .XML file extension from being indexed in the Indexing Options control panel.
Open control panel, click Indexing options–>Advanced–>File Types, scroll to near the end of the list and uncheck XML
esSJae's Virtualization Blog 