doing anything especially raid 0 , where if one hd corrupts or is lost you lose it all, in my opinion is not a good idea. Do it right , in the long run you will be glad you did. You said that you can not defrag your HDs...if that is so. you have to find out why.
click on start / settings / control panel / admin tools / event viewer
then click on system, this is your system log...are there errors ?