Fred, Which model of G4 do you have? Some motherboards will not support dual processors. See this thread for a short discussion and program you can run to check your dual compatibility: <http://forums.macnn.com/showthread.php?t=199701> HTH, Rick On Nov 12, 2005, at 11:43 AM, Fred Kratt (Dynamic Energy Systems) wrote: > I have been using PCs for a long time and recently was given a used > PowerMac G4. I was able to get OSX running on it after buying a new > hard disk. > > > > I tried upgrading to a dual processor given to me by a friend who > is a long time MAC user. > > > > The problem is that the system will not boot up. I get a message in > four languages that says “You must restart your computer…”. > Restarting returns the same message. > > > > Can anybody help me get started?