你在project-------setting------links里加上winmm.lib在文件头部添加#include"mmsystem.h"playsound的相关信息（来自MSDN）PlaySound The PlaySound function plays a sound specified by the given filename, resource, or system event. (A system event may be associated with a sound in the registry or in the WIN.INI file.) BOOL PlaySound( LPCSTR pszSound, HMODULE hmod, DWORD fdwSound );
Parameters pszSound A string that specifies the sound to play. If this parameter is NULL, any currently playing waveform sound is stopped. To stop a non-waveform sound, specify SND_PURGE in the fdwSound parameter. Three flags in fdwSound (SND_ALIAS, SND_FILENAME, and SND_RESOURCE) determine whether the name is interpreted as an alias for a system event, a filename, or a resource identifier. If none of these flags are specified, PlaySound searches the registry or the WIN.INI file for an association with the specified sound name. If an association is found, the sound event is played. If no association is found in the registry, the name is interpreted as a filename. hmod Handle of the executable file that contains the resource to be loaded. This parameter must be NULL unless SND_RESOURCE is specified in fdwSound. fdwSound Flags for playing the sound. The following values are defined: SND_APPLICATION The sound is played using an application-specific association. SND_ALIAS The pszSound parameter is a system-event alias in the registry or the WIN.INI file. Do not use with either SND_FILENAME or SND_RESOURCE. SND_ALIAS_ID The pszSound parameter is a predefined sound identifier. SND_ASYNC The sound is played asynchronously and PlaySound returns immediately after beginning the sound. To terminate an asynchronously played waveform sound, call PlaySound with pszSound set to NULL. SND_FILENAME The pszSound parameter is a filename. SND_LOOP The sound plays repeatedly until PlaySound is called again with the pszSound parameter set to NULL. You must also specify the SND_ASYNC flag to indicate an asynchronous sound event. SND_MEMORY A sound event's file is loaded in RAM. The parameter specified by pszSound must point to an image of a sound in memory. SND_NODEFAULT No default sound event is used. If the sound cannot be found, PlaySound returns silently without playing the default sound. SND_NOSTOP The specified sound event will yield to another sound event that is already playing. If a sound cannot be played because the resource needed to generate that sound is busy playing another sound, the function immediately returns FALSE without playing the requested sound. If this flag is not specified, PlaySound attempts to stop the currently playing sound so that the device can be used to play the new sound. SND_NOWAIT If the driver is busy, return immediately without playing the sound. SND_PURGE Sounds are to be stopped for the calling task. If pszSound is not NULL, all instances of the specified sound are stopped. If pszSound is NULL, all sounds that are playing on behalf of the calling task are stopped. You must also specify the instance handle to stop SND_RESOURCE events. SND_RESOURCE The pszSound parameter is a resource identifier; hmod must identify the instance that contains the resource. SND_SYNC Synchronous playback of a sound event. PlaySound returns after the sound event completes. Return Values Returns TRUE if successful or FALSE otherwise.Res The sound specified by pszSound must fit into available physical memory and be playable by an installed waveform-audio device driver. PlaySound searches the following directories for sound files: the current directory; the Windows directory; the Windows system directory; directories listed in the PATH environment variable; and the list of directories mapped in a network. For more information about the directory search order, see the documentation for the OpenFile function.If it cannot find the specified sound, PlaySound uses the default system event sound entry instead. If the function can find neither the system default entry nor the default sound, it makes no sound and returns FALSE.QuickInfo Windows NT: Requires version 3.1 or later. Windows: Requires Windows 95 or later. Windows CE: Unsupported. Header: Declared in mmsystem.h. Import Library: Use winmm.lib. Unicode: Implemented as Unicode and ANSI versions on Windows NT.See Also Waveform Audio Overview, Waveform Functions 下次遇到这样的问题就看看出错的函数的头加上没有，
The PlaySound function plays a sound specified by the given filename, resource, or system event. (A system event may be associated with a sound in the registry or in the WIN.INI file.) BOOL PlaySound(
LPCSTR pszSound,
HMODULE hmod,
DWORD fdwSound
);
Parameters
pszSound
A string that specifies the sound to play. If this parameter is NULL, any currently playing waveform sound is stopped. To stop a non-waveform sound, specify SND_PURGE in the fdwSound parameter.
Three flags in fdwSound (SND_ALIAS, SND_FILENAME, and SND_RESOURCE) determine whether the name is interpreted as an alias for a system event, a filename, or a resource identifier. If none of these flags are specified, PlaySound searches the registry or the WIN.INI file for an association with the specified sound name. If an association is found, the sound event is played. If no association is found in the registry, the name is interpreted as a filename. hmod
Handle of the executable file that contains the resource to be loaded. This parameter must be NULL unless SND_RESOURCE is specified in fdwSound.
fdwSound
Flags for playing the sound. The following values are defined:
SND_APPLICATION
The sound is played using an application-specific association.
SND_ALIAS
The pszSound parameter is a system-event alias in the registry or the WIN.INI file. Do not use with either SND_FILENAME or SND_RESOURCE.
SND_ALIAS_ID
The pszSound parameter is a predefined sound identifier.
SND_ASYNC
The sound is played asynchronously and PlaySound returns immediately after beginning the sound. To terminate an asynchronously played waveform sound, call PlaySound with pszSound set to NULL.
SND_FILENAME
The pszSound parameter is a filename.
SND_LOOP
The sound plays repeatedly until PlaySound is called again with the pszSound parameter set to NULL. You must also specify the SND_ASYNC flag to indicate an asynchronous sound event.
SND_MEMORY
A sound event's file is loaded in RAM. The parameter specified by pszSound must point to an image of a sound in memory.
SND_NODEFAULT
No default sound event is used. If the sound cannot be found, PlaySound returns silently without playing the default sound.
SND_NOSTOP
The specified sound event will yield to another sound event that is already playing. If a sound cannot be played because the resource needed to generate that sound is busy playing another sound, the function immediately returns FALSE without playing the requested sound.
If this flag is not specified, PlaySound attempts to stop the currently playing sound so that the device can be used to play the new sound. SND_NOWAIT
If the driver is busy, return immediately without playing the sound.
SND_PURGE
Sounds are to be stopped for the calling task. If pszSound is not NULL, all instances of the specified sound are stopped. If pszSound is NULL, all sounds that are playing on behalf of the calling task are stopped.
You must also specify the instance handle to stop SND_RESOURCE events. SND_RESOURCE
The pszSound parameter is a resource identifier; hmod must identify the instance that contains the resource.
SND_SYNC
Synchronous playback of a sound event. PlaySound returns after the sound event completes.
Return Values
Returns TRUE if successful or FALSE otherwise.Res
The sound specified by pszSound must fit into available physical memory and be playable by an installed waveform-audio device driver. PlaySound searches the following directories for sound files: the current directory; the Windows directory; the Windows system directory; directories listed in the PATH environment variable; and the list of directories mapped in a network. For more information about the directory search order, see the documentation for the OpenFile function.If it cannot find the specified sound, PlaySound uses the default system event sound entry instead. If the function can find neither the system default entry nor the default sound, it makes no sound and returns FALSE.QuickInfo
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in mmsystem.h.
Import Library: Use winmm.lib.
Unicode: Implemented as Unicode and ANSI versions on Windows NT.See Also
Waveform Audio Overview, Waveform Functions 下次遇到这样的问题就看看出错的函数的头加上没有，
#include"mmsystem.h"要在#include <windows.h>后面！
因为在它的出错提示中可以看到error LNK2001: unresolved external symbol __imp__PlaySoundW@12,是找不到相应函数的链接，而没有编译错误，说明有函数的声明，在
案<windows.h>中应该已经包含<mmsystem.h>了。
Debug/HelloWin.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.会和UNICODE标记没设置有关吗?