Just so you know, having "nothing on there" has nothing to do with computer speed. Hard drive space is like room left on your CF card in your camera. It doesn't get slower as it fills up.
Also, what programs start up with your computer? Stuff like Quicktime, MSN Messenger, Yahoo messenger (and the like), adobe launcher....all that good stuff....it takes up processing cycles and loads into ram. this takes time.
This is a brand new computer? I'd suggest getting all the latest drivers.
Look for these
Chipset drivers (your chipset is determined by what motherboard you have. It usually says the chipset in the name.)
video drivers (nvidia, ati, or intel most likely makes your graphics. go to their site and download the appropriate driver)
sound drivers (creative, intel, etc...find out what you have and go to their site to download it)
If you need further help, let me know. This is my thing.