OK ...try adding the new hard drive onto the same IDE cable as the origonal hard drive. (instead of the DVD.) The new drive must go in the middle connector.
Now attach the dvd to the ide cable with the cdwr.
Check the Jumpers on the back of all the drives.
C Drive (Master) New Drive (Slave)
CDWR (Master) DVD (Slave)
and as a thought what wattage is your Power Suply Unit..... anything less than 300w will probably be the cause of this.