Here's another alternative:
Create a small partition in the lowest sector addresses on your Caviar 640:
there are several programs available to add partitions, e.g. Partition Magic,
Partition Commander, etc.
Before writing any files in that small partition, turn OFF the Indexing Service on that partition:
My Computer | right-click on that partition | Properties
UNcheck "Allow Indexing Service"
Download the CONTIG program from the Internet:http://technet.microsoft.com/en-us/sysinternals/bb897428.aspx
Create a custom-sized "pagefile.sys" as the first file in that small partition:
a really safe rule of thumb is 1.5X the amount of RAM in your machine.
Change the attributes to "+A +S +H" in Command Prompt:
attrib pagefile.sys +A +S +H
Move your swap file to this pagefile.sys:
right-click My Computer | Properties | Advanced | Performance Settings | Advanced | Virtual Memory
And respond to XP's prompts as you go.
This should "short stroke" all OS I/O to and from that swap file.
You can also run CONTIG without creating a dedicated new partition,
but it won't use "short strokes"; you may want to experiment
by defragging your Caviar 640 after creating "pagefile.sys"
but before moving paging to that file.