[X4U] G5 won't start up

[Jonnythan]

Hello everybody,

I have a 4-year old G5 running OS X 10.5 that refuses to start up - you get
the Apple logo and all looks well, then it shuts down again without going
any further.

This started happening shortly (but not straightaway) after a power cut.
Directly after this the Mac started up but with the fan whirring madly. This
disappeared after a few restarts and was working normally. I thought then it
would be a good idea to run fsck, and after fsck found an error that it
couldn't fix, it now won't start up.

I've tried starting from a DiskWarrior cd by holding down the c-key, but
that doesn't work.

Any ideas, or has the power cut fried something?

Thanks!

Jonathan.