One can not use his horoscope to do this of-course. However you can make sure that the fan inside the PC is rotating. One of the major reasons electronics components fail is due to excessive heat. Hence making sure that the fan rotates can go a long way in making sure PCs upkeep.
Also if the machine is slowing down substantially and if there is hanging problem you should as well suspect that a failure of the hard disk may be impending. There are also tools to check the PC like disk error checking. If bad sectors are observed as a result of disk checks its better to change the disk as a disk with such sectors may be beginning to fail.
Intel recently has started bringing out a temperature monitor and alarm function for the PC. There are also fans available that fit at the bottom of the hard disk so as to reduce the heat around the disk.
as we said earlier, heat is one factor that is primary cause of failures for the current carrying circuitry generally. Hence you must ensure that the PC is always in a cool surrounding. An air conditioner is desirable in places where it is necessary.
Dust free environs would help reduce the accumulation of dust in the system. It is advisable to use the power saving features in the machine to reduce consumption as well as to increase the amount of time the components stay hot.
A UPS would reduce the chances of shutdown of the PC from the power failure as well as protect it from the surge that might destroy the electronics.
Protection against power surges and power failures is important for your computer system. Power surges and spikes are sudden jolts of electricity. They come in to your computer through the electrical line, telephone line, serial cable, parallel cable, or network connection cable attached to your computer.
Power problems such as surges and spike can do nothing or they can cause minor annoyances such as keyboard lockups. More importantly, power problems can cause data loss, or they can fry computer components such as the processor, motherboard, RAM, hard drive, etc..