Good morning:
simple solution .. use knoppix cd in each PC and you're done
> 2. In the centre we do a lot of video editing using Premiere on > window$.> I know some Linux video editing software but the problem is that just > one computer is powerful enough to do the job. If I make cluster out of > few computers then the thing would be strong enough.
Following along on the idea of using a bootable CD the OP might want to take a peek at Dynebolic and Mediainlinux. The packages used in those distros might give some ideas as to the capabilities of the machines in the centre. They are at Distrowatch.
Rob