Resolved (for now)
It was my 24" Dell monitor. The DVI connector appears to be stuffed and will not show the pc up. It was strange as the PC was not making any move to loading (speakers) either. I only found this out after plugging in the wrong monitor at the time (I run dual screens). Now I am on the 19" and it is really really small

After this problem (which involved looking at the CPU to make sure it was not fried), the PC started to turn off by itself. Appears that I did not have the CPU fan on correctly and it must have been overheating and shutting down
Well after a few more hours, I have rebulit the PC again and it appears to be working fine - just testing to see if it stays on after leaving it on for a few hours.
Good news is, I am still within the 1 year that I bought the monitor off Dell so they will no doubt get a call from me on Monday asking for a replacement

Thanks all for your help. The solution was something totally unexpected it appears...