You need Windows XP Shimgvw.dll & the .reg file listed below. Reg file includes support for .BMP/.GIF/.JPG/.PNG/.TIF & the correct default icons for each.
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Copy & Paste everything between (Start) & (End) into a new .reg File.
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Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers]
"C:\\Windows\\System32\\rundll32.exe"="VISTARTM"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers]
"C:\\Windows\\System32\\rundll32.exe"="VISTARTM"
[HKEY_CLASSES_ROOT\.BMP]
@="BMPImage.Document"
[HKEY_CLASSES_ROOT\BMPImage.Document\DefaultIcon]
@="%SystemRoot%\\System32\\imageres.dll,-70"
[HKEY_CLASSES_ROOT\BMPImage.Document\shell\open\command]
@="C:\\Windows\\System32\\rundll32.exe C:\\Windows\\shimgvw.dll,ImageView_Fullscreen %1"
[HKEY_CLASSES_ROOT\.GIF]
@="GIFImage.Document"
[HKEY_CLASSES_ROOT\GIFImage.Document\DefaultIcon]
@="%SystemRoot%\\System32\\imageres.dll,-71"
[HKEY_CLASSES_ROOT\GIFImage.Document\shell\open\command]
@="C:\\Windows\\System32\\rundll32.exe C:\\Windows\\shimgvw.dll,ImageView_Fullscreen %1"
[HKEY_CLASSES_ROOT\.JPG]
@="JPGImage.Document"
[HKEY_CLASSES_ROOT\JPGImage.Document\DefaultIcon]
@="%SystemRoot%\\System32\\imageres.dll,-72"
[HKEY_CLASSES_ROOT\JPGImage.Document\shell\open\command]
@="C:\\Windows\\System32\\rundll32.exe C:\\Windows\\shimgvw.dll,ImageView_Fullscreen %1"
[HKEY_CLASSES_ROOT\.PNG]
@="PNGImage.Document"
[HKEY_CLASSES_ROOT\PNGImage.Document\DefaultIcon]
@="%SystemRoot%\\System32\\imageres.dll,-83"
[HKEY_CLASSES_ROOT\PNGImage.Document\shell\open\command]
@="C:\\Windows\\System32\\rundll32.exe C:\\Windows\\shimgvw.dll,ImageView_Fullscreen %1"
[HKEY_CLASSES_ROOT\.TIF]
@="TIFImage.Document"
[HKEY_CLASSES_ROOT\TIFImage.Document\DefaultIcon]
@="%SystemRoot%\\System32\\imageres.dll,-70"
[HKEY_CLASSES_ROOT\TIFImage.Document\shell\open\command]
@="C:\\Windows\\System32\\rundll32.exe C:\\Windows\\shimgvw.dll,ImageView_Fullscreen %1"
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Drop shimgvw.dll into C:\Windows. Then, right-click the registry file & choose merge. Image viewer should work for all user accounts.
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Vista users: Replace both occurrences of VISTARTM with WINXPSP2 & use that to merge.
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*Updated 1/20/2012: Reg file reduced to minimum & 75% smaller/Now uses system32 rundll32.exe/Vista support added.
What does XP Image viewer do that Windows Vista/7 doesn't? -> Smoothly enlarges pictures, animates GIF files, allows TIF edit.
Click thumbnail below to see full-size picture of what XP image viewer looks like running in Windows 7.