Just to make sure,have you tested the memory and hard drives?try using memtest for the ram and seagtes hdd tester! let us know what you find!

Have you check the hdd?Random freezes and booting errors are most commenly caused by either bad sectors on the hdd or just plain hdd failure! you can even test the memory to make sure! let us know...

This could one of many problems and like lawli56 said the best thing to do first is to check the memory and would even check the hdd for problems! if the hardware checks out you can then try and do...