As in a delay where it comes back or where you have to reset the PC?
The Core2Duo does slow down as it heats up and I don't see where you did your old PC maintenance work. Example at link to follow.
i have an HP Pavilion Desktop(OS VISTA home premium) is hanging all the time.
i installed vmware on my PC ,at that time my RAM(DDR2) was 1GB (2 chips 512/512mb) so i decided to upgrade it with extra chip (2GB) , without knowing if the front side bus is compatible with the motherboard but it was working fine . then i stopped using my PC for 7months . when i started my PC after the 7 months i was really really slow i checked the system properties and there were the shocking news no information about the system memory(RAM) , i shutdown the PC opened the case checked the RAM and installed them again then i closed the case and started my system again . it wasn't fast but better than the first time , the system red the RAM this time but the speed was not good so i decided to install the Vista again and the PC started to hang since that time, the safe mode is working fine , my processor fan is working fine too, tried the check disk no error .
my processor is intel core duo 2 speed 1.95 MHZ (not sure) .
don't know what to do please help T_T