Which encryption software to use ?

I have 20 laptops I want to encrypt. I will be encrypting the whole of the hard disk. They will all be running NT4. I need to be able to administrate it centrally and hold control of passwords etc.. I have been looking at various encryption packagesand have come up with 2 possibilities so far. The first is PC Guardian and the second is Protect Data. Has anyone used these packages before ? Any pro’s/con’s ? Thanks.