My PC has recently become really slow on startup. It gets to the desktop screen and then takes a good minute or two before it lets you do anything. Also I have problems when shutting down sometimes. It sometimes just won't do it at all and hangs on the 'windows is shutting down' screen. Sometimes it just stays on the desktop screen. I have also noticed the fan kicking in quite a lot more than it used to. I have panda platinum security and have done various other spyware and virus checks which don't seem to find anything. Any ideas?