I just created a new RAID 5 array on my Vista 64 computer using 3x 1 TB Western Digital Caviar Blacks Model# WD1001FALS.
It seems to be much slower than I had hoped, I get random momentary freezes also but then the computer will come back.
Here is a link to my computers specs. The Raid is on the Motherboard. System Specs here
I have attached some HD Tune Screenshots. One image is of 1 Single HD with decent speeds.
The next 3 are screen shots of the Raid 5. You can see there is a very wide range of results. During this time of all 3 I only have open firefox and am not doing any major tasks or strains.