Windows has a customizable soundtrack - when different things happen, sounds play.  You can live with the default sounds, turn all the sounds off, or substitute your own sounds.  All configurable via the Sound control panel:

 http://blogs.msdn.com/photos/matthew_van_eerde/images/9020631/original.aspx

You can assign short or long, pleasant or annoying sounds to any event in the list.  For example, you could rip a CD to .wav format and assign it to the "Maximize" event.

There are two events that are a little finicky about how long the sound is, though: the "Exit Windows" and "Windows Logoff" events.  If you assign a sound that is too long to either of these events, it won't play.  It plays when you click the "Test" button, but when you actually log off or shut down, the sound doesn't play.

How long is too long?

Before the answer, a quick review of .wav files.

You can have any number of frames per second.  CDs use a sample rate of 44100 frames per second; DVDs use 48000 frames per second.  This is usually one of (11025, 22050, 44100, 88200, 176400; 48000, 96000, 19200; 8000, 16000, 32000).

You can have any number of samples in a frame: mono (1 channel), stereo (two channels), surround (four channels), 5.1 (six channels), 7.1 (eight channels), or a different number.

Each sample is a number.  This can be a floating-point number (32 bits), an unsigned integer (8 bits), or a signed integer (16 bits, 20 bits, 24 bits, 32 bits.)  The 20 bit and 24 bit integers can be either in 24-bit containers or in 32-bit containers.

The fatness of the samples, and how many there are per second, determines how many bytes a second of .wav data will contain.  The formula is:

bytes/second = (samples/frame, AKA channels) * (frames/second, AKA sample rate) * (bits/sample) / (bits/byte, always 8)

For performance reasons, Windows Vista limits the size of shutdown/logoff sounds to 4 MB.

So how long is 4MB?  Here's the answer in tabular form for most common formats.  Lengths are in seconds.

unsigned 8-bit int

sample rate

mono

stereo

surround

5.1

7.1

8000

524.29

262.14

131.07

87.38

65.54

11025

380.44

190.22

95.11

63.41

47.55

16000

262.14

131.07

65.54

43.69

32.77

22050

190.22

95.11

47.55

31.70

23.78

32000

131.07

65.54

32.77

21.85

16.38

44100

95.11

47.55

23.78

15.85

11.89

48000

87.38

43.69

21.85

14.56

10.92

88200

47.55

23.78

11.89

7.93

5.94

96000

43.69

21.85

10.92

7.28

5.46

176400

23.78

11.89

5.94

3.96

2.97

192000

21.85

10.92

5.46

3.64

2.73







signed 16-bit int

sample rate

mono

stereo

surround

5.1

7.1

8000

262.14

131.07

65.54

43.69

32.77

11025

190.22

95.11

47.55

31.70

23.78

16000

131.07

65.54

32.77

21.85

16.38

22050

95.11

47.55

23.78

15.85

11.89

32000

65.54

32.77

16.38

10.92

8.19

44100

47.55

23.78

11.89

7.93

5.94

48000

43.69

21.85

10.92

7.28

5.46

88200

23.78

11.89

5.94

3.96

2.97

96000

21.85

10.92

5.46

3.64

2.73

176400

11.89

5.94

2.97

1.98

1.49

192000

10.92

5.46

2.73

1.82

1.37







24-bit container: signed 20-bit int or signed 24-bit int

sample rate

mono

stereo

surround

5.1

7.1

8000

174.76

87.38

43.69

29.13

21.85

11025

126.81

63.41

31.70

21.14

15.85

16000

87.38

43.69

21.85

14.56

10.92

22050

63.41

31.70

15.85

10.57

7.93

32000

43.69

21.85

10.92

7.28

5.46

44100

31.70

15.85

7.93

5.28

3.96

48000

29.13

14.56

7.28

4.85

3.64

88200

15.85

7.93

3.96

2.64

1.98

96000

14.56

7.28

3.64

2.43

1.82

176400

7.93

3.96

1.98

1.32

0.99

192000

7.28

3.64

1.82

1.21

0.91







32-bit container: signed 20-bit int, signed 24-bit int, or float32

sample rate

mono

stereo

surround

5.1

7.1

8000

131.07

65.54

32.77

21.85

16.38

11025

95.11

47.55

23.78

15.85

11.89

16000

65.54

32.77

16.38

10.92

8.19

22050

47.55

23.78

11.89

7.93

5.94

32000

32.77

16.38

8.19

5.46

4.10

44100

23.78

11.89

5.94

3.96

2.97

48000

21.85

10.92

5.46

3.64

2.73

88200

11.89

5.94

2.97

1.98

1.49

96000

10.92

5.46

2.73

1.82

1.37

176400

5.94

2.97

1.49

0.99

0.74

192000

5.46

2.73

1.37

0.91

0.68

 

 

The most common audio format by far is 44.1 kHz / stereo / 16-bit; if your .wav file is of this format, you get just under 23 seconds before you hit the 4 MB limit.

If you want to go over this limit, or if you want a multichannel logoff sound, you can get away with downsampling.  If you shoehorn in a longer sound, though, you may run into this:

 http://blogs.msdn.com/photos/matthew_van_eerde/images/9020846/original.aspx

If you just wait, the sound will play to the end and logoff will continue.

If you click "Cancel", explorer.exe will exit anyway and you'll be logged in with no shell.

A trick to get the shell back: Ctrl-Shift-Esc to bring up Task Manager, and File | New Task (Run...) | explorer.exe to reinvoke the shell.  This also allows you to determine which of the notification area icons are well-behaved. :-)