restore the file from windows xp cd, for this you should restore Mmsystem.dll for Winmm.dll, you can find mmsystem.dll in Win95_13.cab file to the Windows\System folder.
1.Click Start, and then click Run.2.Type msconfig, and then press ENTER.3.On the General tab, click Extract File.
In the Specify the system file you would like to restore box, type drive:\windows\path\file (where drive is the drive on which the Windows folder is installed, generally drive C, path is the location in the Windows folder is the destination of the file that you are extracting, and file is the file that you want to extract). 5.Click Start, click Browse, and then locate the Windows installation files, insert the Windows XP cd and then locate the installation files in System folder
6.Click OK, and then follow the instructions on the screen.
Source : Microsoft