In my thread similiar to this one, I have the same problem as you.
I dont know as if these notebooks are real picky or not(I gave the laptop back to the person cause of the problem)
The tech support team at compaq told me to use this.
Below is the partnumber:
40.0GB ATA-100 EIDE hard disk drive - 4,200 RPM, 2.5-inch form factor, 9.5mm height
I never got to try it, cause I didnt want to buy it, and neither did she hah.
but theres maybe a path to try..?
Hope it helps, lemme know, cause if it does I might salvage it