the problem would be one or more of the following scenarios:

- PC starts perfectly fine at some point and time but sometimes it will startup but restarts or reboots again at some point or during normal start up
- PC starts perfectly fine and will run quite some time but will reboot in the middle of an operation or even when it is on idle.
- PC starts and work for quite some time but there are random instances that it will get a "Blue Screen of Death" and suddenly reboots
- PC starts and work fine for some day but there are times that the computer starts up and ends up in a "Blue Screen of Death" then reboots again and the problem starts a new
- PC starts up and operates with no problem until you run a particular or any application that causes a system lockup and reboots the computer
- PC starts up and works perfectly fine but when tried to access or modify shared files from a network computer then it will restart or reboot itself

Common causes why PC are one or more of the following:

- Rusted pins on micro chips embeded on the on the mother board or card peripherals such as PCI cards and AGP cards or even Memory chip (SDR/DDR)
- Rusted or worn out lead linings on the mother board
- Rusted, coroded or worn out contact points on peripheral cards (PCI/AGP and memory chips)
- Bloated capacitors, transistors and moist coming out of one of these is an indication that the board (or atleast part of it) are experiencing power over load
- Soil and foreign materials such as metal filings which are static charge-causing fragments such as rust from other parts of the computer's chasis, hairs and dusts
- Incompatible memory chips (Bus speed versus hardware capacity)
- Incompatible peripheral cards installed on the board
- Damaged power cables integrated in the computer's chasis (especially the colored ones that are often chewed by insects or tiny mice that cleverly gets inside the hood of the computer
- Incompatible power voltages (and not to mention the capacity of the power source outlets <- avoid overloading)
- Poor ventilation or cooling system inside the chasis (this is a rare case though)
- Incompatible BIOS settings versus the device and the programs installed in the computer
- Over clocking that forced the system to it's limits and with the tendency to commit suicide
- Operating system bugs (especially those that are pirated ones)
- Installed programs that has incompatibility issues with certain hardware or operating system
- Installed programs and applications that may have corrupted files or poor installation packages
- Corrupted Registry Settings
- Poor system security programming
- Bad software updates (especially those from Beta ones and Hot Fixes that tries to fix a certain issue but in turn it triggers another issue)
- Improper tweaking of the entire system (whether hardware or software)