Write-behind caching

Write-behind or write-back disk caching initially writes data to RAM (freeing the application to continue immediately, as if the data had been written to disk). The data
are later automatically written to disk (usually within a few seconds) either timed, or when the cache holds a preset percentage of unwritten data. This reduces the
possibility that a problem (such as a power failure) will prevent the data from being successfully written to disk.

Write-through caching always writes directly to disk, ensuring that the application is never tricked into believing that the data are on disk when they may not be. This
results in the highest data integrity, though with slightly reduced performance.

Here are some good sites to check out:

http://www.winguides.com/registry/display.php/221/
http://www.windows-help.net/windows98/tune-36.shtml
http://www.zdnet.co.uk/help/tips/story/0,2802,e7108952,00.html
http://www.tweak3d.net/tweak/win2kmem/

So basically from reading most of those sites, you need to figure out if you need the extra performance of write-behind cache or if you need integrity of the data.  The question is how often are you going to lose power or something like that?  And determine if you need the performance or not.