Problem with i7 and p6t booting

My i7 and ASUS setup has been working fine for the last few months. In my wisdom I decided to overclock the CPU with the stock fan. I got it up to 3.88 I think and it was running fine. I checked the temp and it was all fine too.

When I tried to turn it on today the computer crashed and shut off. Then when I powered it up I got the overclocking failure message then it shut off again. Now it will switch on and stay on (I mean red light on MB comes on all fans, HD, DVD drive etc come on) but the monitors detect no signal! I have no I dea what is going on... I checked the CPU and it looks fine, so I don't think it is fried. Is it a possibility that my Graphics card has gone to pot, or does it sound like the motherboard. The graphics card is quite a few years old and I have had a few problems with monitors not picking up signal from it since I put it in the i7 system, but after a restart it normally works a treat. This time though, no luck at all.

I have ordered a new graphics card so I will find out on Tuesday if it was that but it would be great to know in the meantime to put my mind at rest. I have just forked out loads for the new i7, MB, Ram, PSU etc.

Thanks in advance for any help.