Is this the Compaq Presario 2100 desktop pc or notebook pc? See if this helps:
HP & Compaq hard drive upgrade
Scroll down to ''Step 7: Configure the new hard drive''
I replaced the hard drive in my Compaq Presario 2100 and put in the CD to restore the operating system. It ask for the languange, then I hit next to get to the screen that tells me all my data will be lost and click on that. It looks like it is going to the next screen but it goes from the restore screen to a black one and two words come up 'Eject Disk'. I tried this from a cold start as well (with the CD in the drive) and it did not work. The manual indicates that all I need to do is install the drive and use the software. Can someone help ? Thanks !