You mean, chattering, being accessed constantly with the drive light flickering or on all the time? It's most likely the search indexer. You can either leave the machine alone for an hour or two to finish indexing, or disable the search indexer altogether and use something like Locate or Everything to search instead, however I don't know if either are compatible with Vista 64 bit.
Disable indexing; click here
Locate; click here
Everything; click here
Failing that, I still use AgentRansack; click here