Sound not working PLEASE HELP

[gameaddict8]

Ok well here's the deal. I am running Windows XP on a Compac Presario and my sound is not working but it used to. I recently came back to my grandmother's computer and I found her sound not working when I know it used to. I am not sure if anything was changed while I was away. When I go into Sound and Audio Devices, everything is grayed out under all of the tabs except under Hardware in which I have;
HL-DT-ST RW/DVD GCC-4482B
Audio Codecs
Legacy Audio Drivers
Media Control Devices
Legacy Video Capture Devices
Video Codecs
My audio symbol with the speaker that normally shows up in the lower-right hand corner has dissapeared so I know the computer is not on mute and I've tried to access it in other ways but it will not open or appear. I have also tried the troubleshooting on audio in the computer but they had no answers for me. I have seen other people with similar problems and I have tried some of the posted solutions however none have worked for me. I know you will need my computer specs or something but I do not know how to get those so if someone would tell me how to do that as well it would be appreciated.

[gameaddict8]

Also, I have gone to add hardware and it has detected PCI device but when I try to install it (IDK if there is a disk or not) I get a screen that says cannot install hardware because windows cannot find the neccacary software.
And that's basically what I've got here. I've heard PCI has something to do with sound so I thought this may be the problem.

[ReRun]

On the front of the machine it will say Presario and have a model number, click the link below and type Presario space one time and type that number then click search, it will ask what OS, select XP and you should find the audio driver to download, after it downloads just double click the file and follow the instructions, mostly click yes and next. Reboot when it is dont and post back if the issue is unresolved.http://welcome.hp.com/country/us/en/support.html