I would like you to download (Free) the, Upgrading and Servicing Guide, for the Compaq Presario SR5109UK,
(Will apply to your SR5109 desktop computer),http://h10025.www1.hp.com/ewfrf/wc/manualCategory?lc=en&dlc=en&cc=us&product=3457899&lang=en&
On this page the file is the first one in the list.
Upgrading and Servicing Guide - 2.06MB
Left-click right on the file name.
This is a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on the file name - Upgrading and Servicing Guide, it may take up to 30 seconds before you see the first page.
It may also take longer before the file has fully downloaded.
(Took 4 seconds before I saw the first page, and an additional 20 seconds before the file was fully downloaded. Medium speed DSL connection)
Page 12 has information about removing an Optical Drive. (CD/DVD drive)
Should you not be bale to download this file from HP Support, please state so in a Comment, and I'll lead you through it step by step.
(Computer unplugged from power. The Front Panel has to be removed, and the Side Cover. Then there is a locking arm you swing down to remove an optical drive)