Universal Serial Bus Controller driver problem

In device manager my USB controller has the dreaded yellow question mark!  I've reinstalled the chipset drivers like 10 times both from the dell website and the CD.  It's still not working...  I've heard I need to install the Chipset drivers before anything else.  but... it's too late for that.  and then why isn't there some big neon sign warning you of that?  please help!  i can't plug ANYTHING in to my computer!