Laptop 2.5"HDs Vs PC 3.5"HDs? laptop parts performance?

[Bugsy_malone 666]

Ok so I decided to give myself a bit of a challenge for the new PC I am building, I am fed up of building huge cased monsters and while searching for xbox bits I was supprised to find lots of xbox case bits for sale cheap which gave me an idea!

The idea being to build a PC inside and xbox case, but to a high spec. Doing so will require the use of a few laptop components to get it in the case.

I have a Motherboard that fits, the graphics card will be a challenge, then the Hard Drive/DVDRW drive will be laptop items because of size.

Now one of the puzzling things about laptop hard drives is that they dont come in a standard speed of 7200rpm like 3.5" drives these do, is there a reason for that? I see you can get 4400 rpm, 5400rpm (which one of my previous PCs used and it wasnt fast enough access time for video editing) and 7200rpm.

Now lastnight I was messing about trying out a second hand laptop I aquired which is a toshiba satilite pro 6000 model, as standard it came with a CD rom drive and a 20gb HD, I managed to win a DVD/CDRW drive off ebay the other day for about 8 quid for it and installed it lastnight along with some DVD viewing software as I thought the best way to test the drive is to watch a film, problem was it didnt seem to read quite fast enough I dont think as the film would play a few seconds then be reading and then playing meaning that the film wasnt running smooth. Now to me I think it is setup, but could it be to do with laptop hard drive speed? or a faulty DVD drive? (its running XP pro at the moment)

What I want to try and do is use a laptop DVD drive (although I will buy new not used) and a 160/250gb laptop hard drive to help fit the bits in my case, but i dont want to get the wrong parts or waste my time if the laptop parts wont be upto doing a spot of heavy graphics gaming/watching films/maybe video editing.

Being a bit confused I thought I'd ask here