Here are the links to support pages for the major PC manufacturers and software.

Microsoft TechNet(http://www.microsoft.com/technet/default.mspx)
HP and Compaq (http://welcome.hp.com/country/us/en/support.html)
Dell (http://support.dell.com)
Gateway (http://support.gateway.com/support/default.asp)
Toshiba (http://www.csd.toshiba.com/cgi-bin/tais/su/su_sc_home.jsp)
Sony (http://www.ita.sel.sony.com/B2B/support/index.htm)