The tool is very small in size (130Kb) and required 10 MB of free hard drive space. After installing, it will sit on your system tray. Just open it and select available CD/DVD drive and move it to locked CD/DVD drive to lock it.
CD/DVD Drive Locker is free tool for Windows Vista and XP that helps to temporarily turn off the CD/DVD drive and so pressing on the CD/DVD drive's buttons doesn't lead to the drive being ejected. This is especially useful to keep the children away opening the CD/DVD tray.