[X4U] How much can it cost

[Paul Moortgat]

My G5/2.5 suddenly turned into a vacuum cleaner yesterday evening and  
got frozen.  I restarted and all worked well.
This morning I woke the G5 and had a black screen, and when I  
restarted I got a black screen again.
Then I restarted with opt-comm-shift-del to use my external backup  
wich worked.  Then I could insert my DW disk and restarted holding the  
"C".
I repaired my internal disk, restarted and then did the latest upgrade  
to 10.5.3.  All seemed to work.  After 10 minutes I got that vacuum  
cleaner sound again.
After that I no longer can use the internal HD, nor the external.  I  
replaced the internal with a not so old drive with Tiger and this also  
doesn't work.
Nothing will work.  I keep that black screen most of the time, or when  
it goes a little further, I get the Apple logo, but that's all.  There  
it stops.
Now I work from the external HD (10.5.2) hooked to my PB 867 chosen as  
startup HD.  I just did a backup a few days ago, but I'm sure that the  
internal HD in the G5 is OK.
The G5 is 3.5 year old.  In my opinion it can be two things.  The  
motherboard is gone, or not so obvious, the battery is empty.  Can it  
be that the battery is out of order?
And will the G5 no longer work with a broken or empty battery?
When it should be the motherboard, how much can that cost?

P.S.  Writing on this PB is slooooooow.  And I was so pleased with the  
speed when I got it.

Paul Moortgat