You should be able to grab it from the Windows CD:
To resolve this issue, extract a new copy of Sndvol32.exe from the Windows XP compact disc to the system_root\System32 folder on your computer's hard disk. To do this, follow these steps:
1. Insert the Windows XP CD-ROM into your computer's CD-ROM or DVD-ROM drive. Press and hold down the SHIFT key as you insert the CD-ROM to prevent it from starting automatically.
2. Click Start, and then click Run.
3. In the Open box, type cmd, and then click OK.
4. Type the following lines at the command prompt, pressing ENTER after each line, where CD-ROM drive is the drive letter of the computer's CD-ROM or DVD-ROM drive that contains the Windows XP CD-ROM, and system_root is the path and folder name where the Windows system files are located (generally C:\Windows):
expand sndvol32.ex_ system_root\system32\sndvol32.exe
Note that there is a space between "ex_" and "system_root" in this command.
For example, if your computer's CD-ROM drive is drive E, and the folder that contains the Windows system files is C:\Windows, type the following lines at the command prompt (pressing ENTER after each line):
expand sndvol32.ex_ c:\windows\system32\sndvol32.exe
5. Type exit to quit the command prompt.
6. Verify that you can start Volume Control and that the Volume icon is displayed in the notification area (if you selected this option).