com auto shut down after afew hour. (1-3 hours) could it be the harddisk prob?as it gain heat fast to make the whole harddisk hot..

Heat will certainly cause shutdown problems. If you can move the hard disk to a different location within the enclosure to provide more "air space" around the disk, it would help. Also an additional cabinet cooling fan will probably help.

Ensure your CPU fan/heatsink assembly isn't clogged with dust.

thanks !!!Dan tat's help mi alot...