I have done the task manager bit and there is nothing that should not be there, ( no extra programmes running) and have checked the power options and they seem to be ok. Someone said there may be a faulty connection with the mouse ( the bit where the mouse connects into the computer) and the reason it will not switch off, is because it is looking for the mouse when it closes down and cant find it and that is why it will not close down normally. I am not too worried about it now that I have my computer up and running again, will just continue to close down via pushing the button.

You may be right about the mouse connection, when you close down windows, you see the message "saving settings", this is so when windows starts up the next time to your previous settings.
Check your mouse and k/board connectors again, also, you have an old m/board, some of the oldies don't like USB mice - k/boards

You could try your power options again.

In control panel click Performance and Maintenance, and then click Power options.
Click the APM tab.
Check to select the Enable Advanced Power Management Support check box, and then click OK..If it is allready checked, then try unchecking it.
Also. do you have sp2 installed?(service pack 2) check by right clicking on "my computer" on your desktop and select properties on the menu...Try leaving your cd-drive drawer open or leave a cd inside while you shutdown.....

Go into device manager and check if there are any yellow exclamation marks showing under any hardware.

You should really try resolve this shutdown issue rather than using the power button on your pc constantly ,or you could end up with more problems on your pc. ...And as i said before there could be many other causes ...