New PC won't boot off anything.

Firstly, in an attempt to keep everybody happy, I'm going to delete
the post I'm following up and just have what I write from now on im my
own posts.
Tom, as I mentioned, I have a second chassis with a 400W power supply.
I'm only powering the bare bones, i.e. mobo, P4 chip, heatsink fan,
memory, graphics card and hard drive. It's my understanding, please
correct me if I'm wrong, that this is more than adequate.

At this stage all my hardware seems to be working but the only thing I
can't test is the Socket 423 Pentium 4 chip so I've ordered another
one.

Thanks for you help guys.

Guys,

Finally I've put this annoying issue to bed. It turned out to be yet
another faulty P4 chip. I received the new one in the post and
installed it, the machine booted right away.

I just like to say a big sincere thanks to all you guys who responded
with your suggestions.

Alan.
Happy gamer at last.