To Enable to play multi ICQ
[HKEY_CURRENT_USER\Software\Mirabilis\ICQ\DefaultPrefs]
"Multiinstance"="Yes"

To enable download 2 or more files at the same time.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"MaxConnectionsPerServer"=dword:00000008
"MaxConnectionsPer1_0Server"=dword:00000008

To enable auto reflash.
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Update]
"UpdateMode"=hex:00

To Disable Desktop.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDesktop"=dword:00000001

Clear Document History on shutdown windows.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"ClearRecentDocsOnExit"=dword:00000001

Turn off Document History.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoRecentDocsHistory"=dword:00000001

Hide Documents on Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoRecentDocsMenu"=dword:00000001

Hide drives on My Computer.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDrives"=dword:HHHHHHHH
H = Hex number
1 - hide A:\
2 - hide B:\
4 - hide C:\
8 - hide D:\
16 - hide E:\
32 - hide F:\
64 - hide G:\
and so on ... to Z:\
If you want to hide C:\ D:\ and E:\
H = 4 + 8 + 16 = 28 = 1C (in Hex)
Example: "NoDrives"=dword:0000001C

Hide Run in Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoFind"=dword:00000001

Hide network Icon.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoNetHood"=dword:00000001

Hide Favorites Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoFavoritesMenu"=dword:00000001

Hide Log Off in Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoLogOff"=dword:00000001

Hide Shutdown in Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoClose"=dword:00000001

Hide Search in Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoFind"=dword:00000001

Disallow Add printer driver.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoAddPrinter"=dword:00000001

Increase Start Menu speed.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"MenuShowDelay"="0"

Increase Shutdown speed.
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Shutdown]
"FastReboot"="1"

Disallow Active Desktop.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoSetActiveDesktop"=hex:01,00,00,00

Disallow save setting.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoSaveSettings"=dword:00000001

Disallow save/change folder setting.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoSetFolders"=dword:00000001

Disallow save/change Taskbar setting.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoSetTaskbar"=dword:00000001

Disallow delete printer driver.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDeletePrinter"=dword:00000001

Hide printer tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoPrinterTabs"=dword:00000001

Hide Background tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDispBackgroundPage"=dword:00000001

Hide Screen Saver tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDispScrSavPage"=dword:00000001

Hide Appearance tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDispAppearancePage"=dword:00000001

Hide Display Setting tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDispSettingsPage"=dword:00000001

Disable Windows Update.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoWindowsUpdate"=hex:01,00,00,00

Disable Some program to run under windows.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"RestrictRun"=dword:00000001
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\RestrictRun]
"1"="notepad.exe"
"2"="regedit.exe"
The setting mean only "notepad.exe" and "regedit.exe" is runable.

Disable using Regedit.exe.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
"DisableRegistryTools"=dword:00000001

Change the Desktop Icon size.
[HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics]
"Shell Icon Size"="40"

Change the skins of Internet Explorer.
[HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Toolbar]
"BackBitmapIE5"="filename.bmp"
"BackBitmapShell"="filename.bmp"

Other setting, to hidden some others tab.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
"NoAdminPage"=dword:00000000
"NoConfigPage"=dword:00000000
"NoDevMgrPage"=dword:00000000
"NoDispCPL"=dword:00000000
"NoFileSysPage"=dword:00000000
"NoProfilePage"=dword:00000000
"NoPwdPage"=dword:00000000
"NoSecCPL"=dword:00000000
"NoVirtMemPage"=dword:00000000

* note *
Editing Registry is not recommend for computer beginner and be careful when editing Registry setting. It will damage your computer if you accidentally deleted some important value or data.
Some of these registry may not work on Windows NT/2000/XP.