Start by testing your Memory http://www.memtest86.com/download.html
Then if you can test your GPU in a different computer. I have never lost a computer component on a hard reboot.
i dont know how to install that its not a regular program installer. any alternative to memtest?
The thing to fix first is the freezing while playing games.
This is happening because either:
your PSU is weak
you graphics card is overheating
your cpu is overheating
you overclocked something too far (usually means not enough volts or just too dang far)
Run gpuz (or some other program) to see what your GPU is doing, then run another tool like CPUID to see what your CPU is doing.
Did you change something - new memory, new graphics, and then these problems started?
A good quality power supply will not hurt your components by pushing the front power button, who can say for a poor one.
my psu is corsair 750w
my graphics card becomes 81 celcius on load
my cpu 22 celcius on load (i got a nice fan for it)
i didnt overclock anything
this freezing problem started happening when i ran a intense program which caused my comp to freeze. since then, my comp has been always freezing whenever i started playing games. the funny thing is. my comp always freezes ONCE when i start playing a game. but after that, for the rest of the day, i dont freeze anymore even playing games. so i always freeze once a day.