If your computer is constantly restarting, blue screening or just being crabby in general. it may be the motherboard. The motherboard is a core component of a computer. Just Google the term "motherboard" or "mainboard" and you'll get an idea of what one looks like. I'd argue that the motherboard is 'the' core component of a computer but without a processor and memory the motherboard is non-functional.

A swollen capacitor alone is enough to cause a computer to act weird, with lotsa restarting, blue screens, and a myriad of other problems like your CD ROM doesn't read CD's anymore. A busted capacitor is like a battery that has swollen open and leaks acid all over everything. See image at left. If you have capacitors in your computer that look like this you'll have to either replace the mainboard or replace the computer. Replacing capacitors is generally not an option for a number of reasons like, finding the right capacitor, knowing how to take out the leaking capacitor, install the new and test that they are indeed working.