iBook G4 problem

I recently had to replace my DC-in Board, i followed the instructions on the web and was expecting everything to be good.

It wasnt.

Ever since i have had a number of problems including:-

1 9/10 times the computer does not boot up and i can hear the fan spinning very loudly.
2 When it does boot up it will work for a time and then either the screen fades to white slowly or the screen gets scrambled.
3 The other day it had a Kernel Panic.

So on the advice of various people i tried to run the disk repair - didnt work
i then tried reformatting my hard drive and now i cant get the thing on long enough to reload OSX

Does any body have any ideas as to waht has happened because i really cant afford to send it back to apple.

System info:-

Apple iBook G4 14.1"
933mhz
40 GB HDD - now empty
was running on 10.4.9 upgraded from 10.3 about a year ago

Thank you in advance

oli

have tried to reset the PMU and that worked that got it to boot up but the screen started playing up again

Thank you for the help any other clues?