IMac G5 - hang on start-up with roaring fans

Question

Hi all
Problem occured after trying to instal CD that came with WD-external hard disk 250Gb.
My friends iMac G5 will not cont when starting-up after showing the Apple.
• Showing Apple and moving it slightly down with a jump (less than 1cm)
• No rotating wheel-pinns ???
• Roaring fans
• No progress (at least for 20 min)
Starting from an external hard disk. Keeping alt down during start-up. Works nicely.
Selecting it as start disk - works OK
Running:
• Repair performances - (Apple Disk Util tool) - no effect
• Repair hard disk - (Apple Disk Util tool) - no effect
• DiskWarrior™ - no effect
• TechTools - no effect
What can have happened to the internal hard disk. All files are there and can be use via external
hard disk.
Track zero - error ?
Yours in need of help. Bengt W

Answer 1

Which "model" & "generation" G5 iMac does your friend have?
Need this info so that the knowledgeable users can provide you/friend with the proper troubleshooting solution(s).
http://docs.info.apple.com/article.html?artnum=301724-en How to identify your iMac
http://docs.info.apple.com/article.html?path=Mac/10.4/en/mh355.html Getting information about your computer
You can have this info displayed on the bottom of every post by going to 'My Settings' which is located in the column on the right under your name, and filling in the information asked for.
Thank you
In the meantime, see the following Knowledge Base Articles:
http://docs.info.apple.com/article.html?artnum=301287 My computer stops responding during startup
http://docs.info.apple.com/article.html?artnum=301733 iMac G5: How to Reset the SMU (iMac G5, the iMac G5 (Ambient Light Sensor), and the iMac G5 (iSight)).