Hi scottev, have you referred to the troubleshooting documents provided by Sparkles1 above? If that doesn't resolve it, you may have to get your fan replaced. In which case you can call support for your options.
HP technical support: 800-474-6836. If you live outside the US/Canada Region please click the link below to get the support number for your region. http://www.hp.com/cgi-bin/hpsupport/index.pl