COMPUTER FREEZES or wont boot up

Common causes:

1.) Bad Powersupply or failing...

2.) underpowered Powersupply...

3.) Buldging or leaking Capacitors... http://en.wikipedia.org/wiki/Capacitor_plague

4.) corrosion, ie. the contacts of the RAM or GFX Card... Reseat RAM and GFX Card after cleaning the contact points with a Nr.02 pencil erasor...