need a little help with a G4 please

hi all,
i recently came across several macs.the first one i am working on is a G4 running 9.2.a little history on these computers.they were in an office hooked to a network.they were always on the internet.no spybot or adware removel programs have been run.norton utilities was run at some time.
it will boot all the way to the desktop.the mouse will move around the screen but that's it.when i click on any of the icons nothing happens.i have to shut it down by unplugging it.
could some of the memory be bad.any suggestions would be greatly appreciated.

thanks,
mike

i am new to the mac world,so be gentle

sounds like a possible extension conflict. have you installed any hardware or software on it recently? try starting up holding shift to boot without extensions, if this works, use extension manager to turn off the conflicting extensions.