On installing Windows XP and 2000 on a fresh new machine, the default sound codecs are installed for each sound device that will play sound in that Windows machine. However, if Windows does not detect a sound card, these codes might not be installed at this point. So, if you were to install a sound device and/or a sound card later on, your sound card driver might not detect these default codecs and/or install them if required. This is true for most low-end sound card drivers.

Thus, most likely, there will be no sound output from your system. To check if your system is undergoing a missing sound codec situation, go to Control Panel -> Sound and Audio Controllers, and then click on Hardware tab. Then select the Audio Codecs entry and click on Properties tab. If you have this error and you can’t hear any sound, you will most likely find only about a couple of codecs entered in the listing, particularly if you have not applied a registry patch to fix the issue. Actually, even a registry patch can’t fix this problem if the *.acm files are missing.

However, you can manually install the required codecs – just follow the steps given below.

· Click on Start -> Control Panel.

· Click on Add hardware applet.

· On the Add Hardware Wizard, click Next.

· Select “Yes, I have already connected the hardware” radio button and then click Next.

· Choose “Add a new hardware device” at the bottom of the list and then click Next.

· Select “Install the hardware that I manually select from a list (Advanced)” and click Next.

· Select “Sound, video and game controllers” from “Common hardware types” list and click Next.

· Select “(Standard system devices)” from “Manufacturer”.

Note: To install or reintall video codecs, select “(Standard system devices)”  from “Manufacturer” and “Video Codecs”  from “Model” instead.

· Click on “Have Disk…” button.

· Click Browse button in the Install From Disk dialog box. Navigate to folder C:\Windows\System32, and then locate mmdriver.inf file. Highlight mmdriver.inf and click Open or simply double click on mmdriver.inf file, then click OK in the Install From Disk dialog box.

Click on “Continue Anyway” button if a warning about logo compatibility pops up.

· A list of audio codecs supported by mmdriver.inf appears on the Add Hardware Wizard.

· Select a codec that you want to install. All codecs that you want must be installed one by one. Select one of the codecs needed such as Microsoft IMA ADPCM Audio Codec, and click on Next to reinstall the codec (on install the new codec is not yet be installed). MCI drivers are not needed as these are legacy drivers for Windows 95/98/Me.

Windows XP or 2000 installation CD may be need.

· Repeat the steps to install other drivers until all is installed completed.

· Reboot computer.

The following table lists the codecs that commonly included with original Windows installation:

1-)Download latest version of ATIFlash utility.
2-)Copy it to a flash memory + your original BIOS file and BIOS file you want to flash to your card.
3-)Boot your PC using a Windows 98 or ME CD, you'll see a DOS screen with few options.Choose start with CD-Rom support among these options and wait a few secs. When you're enable to type, reach your USB stick using DOS commands, run atiflash.exe with appropriate commands.

Detailed information is given in the posts above ^.

Edit:Oh i forget to say the most important thing: never restart your computer if flashing process fails. try to reflash to original BIOS in case it fails. it is a good idea to do this on a backup or onboard GPU.