It sounds like you need to install audio drivers. If you right click on "My Computer" and go to "properties" Then the hardware tab at the top then "Device Manager" look for any "unknown devices" with big yellow question marks (?) next to them.
These devices will all require drivers. The first step is to double click on them then click "re-install driver" click "Yes this time only" when asked about connecting to windows update and make sure you are connected to the internet. Click next and then click "Install automatically" or something along those lines *not* the "manually" option.
If you are lucky you will now automatically install the drivers. It will say this is happening which is good. If however it says it cant find any drivers just close that window and move on to the next device that is unknown.
If you still have drivers missing go to windows update (start menu, all programs then right at the top) when asked choose the "custom" option and once it has checked for updated see if there are any on the left under "Hardware" it will saw "Hardware(5)" or some other number. If its 0 then its down to manual installation. But if it has a number above zero click it and check the drivers you need (they will mention audio, video, ethernet, wireless etc... in the name of the update i expect)
then click on the install updates button jsut above the "hardware" link. Follow it through and install them, restart and see how you stand.
for manual installation go back to device manager, double click the device you want to install drivers for and go to the "details" tab at the top. In the drop down box select "Device instance Id" and you will see a string of worsds, slashes and numbers like "PCI\VEN_1002&DEV_12345&SUBSYS_blah...." The important part is the bit *before* "&SUBSYS" or "&REV".
Basically this string means the following: "PCI\" means its a PCI card "VEN_1002" means it comes from a vendor with the code "1002" and "DEV" is the device code. So in my example above you just need the bit that says "PCI\VEN_1002&DEV_12345" Type that into google (i mean the codes you find on your system, not what ive typed here) and add the word "drivers" afterwards, eg: "PCI\VEN_1002&DEV_12345 drivers"
You'll now see lots of crap pages about how they can solve your problem, probably with "Driver detective" well they cant. But you need to find the name of that device, it will be in one of the results, just a keyword like "dell" "Ati" or whatever, you need to piece it together to find the name of your device, or at least the manufacturer. Then you can google the name of the driver you need eg "ATI graphics driver" or whatever it turns out to be, download it and install it and you should be good.
Its a little confusing but its not difficult. Good luck!
PS: One last thing to try is to google the name of your PC eg "HP minitower 2250 xp drivers" but of course use the model of your pc, not the hp stuff. You might find that the manufacturer has a driver page for each pc they make so you can just look under the sound, audio, network etc... sections and download the drivers from there. In fact, id try this step first

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