If your computer is getting old..
You can waste hours and even days trying to get something to work, but working with physically defective and/or old hardware and incompatible software will always end in tears.
If you pick up a virus/Trojan/worm..
Eliminating virus infections is not as easy as it once was. Virus writers aim for maximum operating system destruction these days. You can be 'macho' about them and try to get rid of them piece by piece, or you can re-install.
A re-install is NOT the easy way out, but it is the best way to ensure that there is no virus infection left in the computer. This is particularly important if you fall victim to a 'telephone' scam and allow the caller remote access to your computer.
Staying out of trouble..
If you want trouble free computing, don't believe 'too good to be true' claims, don't mess with registry or system settings, and don't overclock your hardware.
Note that the weakest part of a computer system is not always an internal part.. :-)
I have been a Microsoft MVP since 2005..
Have a great day..
"The trouble with 'marvels' of modern technology is that they require 'marbles' if one is to realise the full potential"