Video editing.
That may be something I know a little about.
The overall speed difference between ATA100 and ATA133 will most likely be negligable for "feel". A lot of benchmarks do show a small difference but overall it is negligable.
The old saying goes that you are only as good as your weakest link. Nevermind if the controller is ATA133 or not...the two disks will run at ATA100 speeds. On the EIDE level this will not be a concern vs. ATA133.
My strongest suggestion is to run the programs and OS off a single disk with the VIDEO disk as the
RAID 0 array. It isn't the OS and programs that need blazing speed...it is the raw video data that must be read from/written to the disks.
As always dual processors will assist greatly with effect and timeline rendering and a third party card such as the Matrox RTX10 or RTX100 will be of a greater benefit. The video card does not play as paramount role in video editing compared to that of gaming.
Want to know more?
Read this.
Hope this helps.

And welcome to the forums.