You may want them on a different drive than your system and off your D drive for efficiency and security. One recommendation I've heard is to put logs on a mirrored disk set and the Web contents on a strip set. I haven't done any benchmarking on logging overheard. When the logging cache gets full, the cache gets flushed to disk. You can't control how often that occurs and logs must be on the local drives as they may be written out under the security context of the system account which can't access the network.
Some people think logging is adds neglible overhead.
Others think you need to think about optimizing logs for writing to mitigate the performance hit. The point is, think about how you want to setup your server before you start accepting the defaults. A word on the NT role. If you install IIS on a domain controller, consider making it a unique domain. It is not generally recommended to install an IIS server on an active domain controller.