It'll all be handled by the drive controller so it won't impact your CPU performance at all, and if it does it'll most likely be a completely negligible difference anyway.

As for partioning I'd recommend you really don't. Marking of a 1gig partition for the Windows temp file makes a hell of a lot of sense, as it avoids the temp file cluttering up and fragmenting your drive.

Apart from that I would only recomend paritioning a drive if you intend to have two different OS installs on the same hard drive. There is no real benefit to partitioning your drive beyond that, a lot of people make different partitions for to collect different files together. You know that kind of makes sense until you realise that if you fill one partition up you are screwed, as you have to put the files somewhere else which destroys the usefullness of your partion setup. Or you could just do the sensible thing and put them in folders which are dynamic in size. Just have a "Random" folder for random unorganised files, it's much easier and flexable than setting aside a particulr space.