CPU FAN Did this ever happened to you?

that not bad as dust is on older pc. if you have a vac or air pump that blows air just blow it out. i would start with a hirem boot cd and boot from it. run anti virus scan and then hdtune or hard drive test. hard drives do have a set life and they can cause a pc to slow down when they start to die/age. i would also run memtest to see if his ram is fine. also use ccleaner and a good defrag. also use msconfig and turn off unneeded programs at start up. with windows sometime is it a good thing to nuke and pave it every some many years. (wipe the hard drive and start fresh). I would use a ext hard drive and move his personal data to it then run the desktop restore cd. depending on the age of the pc..at some point you do need to say dude this system is too old to do what you want..time to replace it with a newer system.