[Jonathan90]

looks as if your pc is overheating m8 thats why it don't come on straight away needs to cool down

omg dude just realised x800 i ahd the exact same card and i used to get that shutdown overheating

my advise download hwmonitor from cpuid

monitor temps

those cards run very hot i mean hot they can easily bump the temp inside the case to a poin were it shutsdown to prevent damage