Disable menu animations
To disable menu animations (sliding in/out) and speed up performance of the UI a bit:
HKLM\SYSTEM\GWE\Menu\AniType = 0 (DWORD decimal)

To change it back to the default:
HKLM\SYSTEM\GWE\Menu\AniType = 6 (DWORD decimal) 


Pocket IE to Version 5.5 (For Secured Sites)
1)  Go to the HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\User Agent\ key.
2) Set the default value to "Mozilla/4.0" (Default is "Mozilla/2.0").
3) Set the "Version" value to "MSIE 5.5" (Default is "MSIE 3.02").
4) Set the "Platform" value to "Windows NT 5.0" (Default is "Windows CE").
This will only work on some secure sites that check version number rather than perform a check for support of secured transactions.

This registry hack will make Pocket Internet Explorer identify itself as IE 5.5 on Windows 2000. However it will prevent web sites that provide Pocket PC specific content to be able to know you're actually using a Pocket PC.

Change the Tap & Hold Dots Color
1) Go to the HKLM\SOFTWARE\Microsoft\Color\ key.
2) Add a Binary value called "40" if it does not already exist.
3) Set the value to "rr gg bb 00" (RGB hex values 00 to FF so "FF 00 00 00" is Red), (RGB hex values 00 to FF so "00 FF 00 00" is Green), (RGB hex values 00 to FF so "00 00 FF 00" is Blue).
 
Speed up your Display (Faster opening programs/menus)
1) Browse to HKEY_LOCAL_MACHINE\SYSTEM\GDI\GLYPHCACHE\Change the "limit" value :
2.1) 4096 : this will slow down the display, but use less memory
2.2) 8192 : this is the default value on Pocket PC, average memory/performances
2.3) 16384 : this will speed up the display, but use more memory, twice the default Pocket PC value
2.4) 32768 : Or even more
3) Reboot

Change the width and height of scroll bars
1) Browse to \HKLM\SYSTEM\GWE\
2) cyHScr : Horizontal Scrollbars Height in pixels (default is 13)
3) cxHScr : Horizontal Scrollbars Width in pixels (default is 20)
4) cyVScr : Vertical Scrollbars Height in pixels (default is 20)
5) cxVScr : Vertical Scrollbars Width in pixels (default is 13)
6) Reboot

Improve call quality
(applied to my Wizard, otherwise the person on the other end of the line says I sound too quiet).

HKEY_LOCAL_MACHINE\SOFTWARE\HTC\AUDIOGAIN 
EARPHONE_UPLINK_VOLUME "AA" 
RECEIVE_UPLINK_VOLUME "AA" 

HKEY_LOCAL_MACHINE\SOFTWARE\HTC\AUDIOGAIN0 
EARPHONE_UPLINK_VOLUME "AA" 
RECEIVE_UPLINK_VOLUME "AA" 

HKEY_LOCAL_MACHINE\SOFTWARE\HTC\AUDIOGAIN1 
EARPHONE_UPLINK_VOLUME "AA" 
RECEIVE_UPLINK_VOLUME "AA" 

HKEY_LOCAL_MACHINE\SOFTWARE\HTC\AUDIOGAIN2 
EARPHONE_UPLINK_VOLUME "AA" 
RECEIVE_UPLINK_VOLUME "AA"


MMS configuration and came at this change: 
people who are having problem with MMS configuration must apply the tweak below (people who have upgraded to WM6 this is tweak for MMS) after installing the MMS cab file (you can get it here) the apply the below change and it will solve your problem.
instead of gateway: 216.155.165.050 ... use gateway: 216.155.165.50 
u see the zero of 50 is gone so just do this and see if it works !!

Disable window animations
To disable window animations (minimizing/maximizing) and speed up performance of the UI a bit:
HKLM\SYSTEM\GWE\Animate = 0 (DWORD decimal)

And to switch them back on:

HKLM\SYSTEM\GWE\Animate = 1 (DWORD decimal)

Increase font cache
To increase the font cache, speeding up font rendering at the cost of a bit of memory:
HKLM\SYSTEM\GDI\GLYPHCACHE\limit = 16384 (DWORD decimal)

To change it back to the default:
HKLM\SYSTEM\GDI\GLYPHCACHE\limit = 8192 (DWORD decimal)

You can set the value to pretty much anything you like, but suggested values are 4096, 8192, 16384 & 32768.

Enable FileSystem cache
To enable the FileSystem cache, speeding up overall performance at the risk of the cache not being written on a sudden reset:
HKLM\System\StorageManager\FATFS\EnableCache = 1 (DWORD decimal)

To disable again:
HKLM\System\StorageManager\FATFS\EnableCache = 0 (DWORD decimal)

Note that by default, the cache size is zero, and you will see no effect. See "Increase FileSystem cache" below to increase the cache size.

Increase FileSystem cache
To increase the file system cache:
HKLM\System\StorageManager\FATFS\CacheSize = 4096 (DWORD decimal)

To return the file system cache to zero:
HKLM\System\StorageManager\FATFS\CacheSize = 0 (DWORD decimal)

You can set the value to pretty much anything you like.

Increase FileSystem filter cache
To enable the file system filter cache, speeding up overall performance with file mangement:
HKLM\System\StorageManager\Filters\fsreplxfilt\ReplStoreCacheSize = 4096 (DWORD decimal)

To return the file system filter cache to zero:
HKLM\System\StorageManager\Filters\fsreplxfilt\ReplStoreCacheSize = 0 (DWORD decimal) 

 
File Locations : 

Change the location of My Documents
Documents are opened in and saved to the device's internal storage by default. You can change this location to, for example, your Storage Card:
HKLM\Software\Microsoft\Windows CE Services\FileSyncPath = "\Storage Card\My Documents" (REG_SZ string, no quotes)

To return to the original location:
HKLM\Software\Microsoft\Windows CE Services\FileSyncPath = "\My Documents" (REG_SZ string, no quotes)

Change the location of email and attachments
When reading and sending email in Pocket Outlook, emails and their attachments are saved in the device's internal storage by default. You can change this location to, for example, your Storage Card:
HKCU\Software\Microsoft\MAPI\PropertyPath = "\Storage Card\Mail" (REG_SZ string, no quotes) HKCU\Software\Microsoft\MAPI\AttachPath = "\Storage Card\Mail\Attachments" (REG_SZ string, no quotes)

To return to the original location:
Just simply delete these Registry settings (since neither is included by default).

Change the location of Temporary Internet Files
When browsing the web, pages and images are saved in the 'Temporary Internet Files' location. You can change this location to, for example, your Storage Card:
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders\Cache = "\Storage Card\cacheie" (REG_SZ string, no quotes)

To return to the original location:
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders\Cache = "\Windows\Profiles\guest\Temporary Internet Files" (REG_SZ string, no quotes)

Change the location of Ringtone file storage
WM5 will look for Ringtones in \Windows\ or \Windows\Rings by default. You can change this location to, for example, your Storage Card (example given is for ringtones placed on the Storage Card root folder)
HKCU\ControlPanel\?SoundCategories\Ring\Directory = "\Storage Card\" (REG_SZ string, no quotes)

To return to the original location:
HKCU\ControlPanel\?SoundCategories\Ring\Directory = "\Windows\Rings\" (REG_SZ string, no quotes)

Note the default location may be "\Windows\" or "\Windows\Rings\" depending on your Device provider.

Make WM5 ask where to install a program (1)
If you wish to be able to specify whether to install a program on WM5's Main storage, or your Storage Card, regardless of installer setting set:
HKLM\Software\apps\Microsoft Application Installer\fAskDest = 1 (DWORD decimal)

To disable again:
HKLM\Software\apps\Microsoft Application Installer\fAskDest = 0 (DWORD decimal)

Please note that many applications do not support being installed on the Storage Card and may behave unpredictably, including crashing.

Make WM5 ask where to install a program (2)
An alternative method of making WM5 ask where to install a program is by adding the "/askdest" option to the Windows CE loader:
HKCR\cabfile\Shell\open\command = 'wceload.exe "%1" /askdest' (REG_SZ string, no quotes)

Make WM5 keep CAB files around after installing (1)

If you wish to keep the original .CAB file around after installing the application, set:
HKLM\Software\apps\Microsoft Application Installer\nDynamicDelete = 0 (DWORD decimal)

Or to restore to the default:
HKLM\Software\apps\Microsoft Application Installer\nDynamicDelete = 2 (DWORD decimal)

Make WM5 keep CAB files around after installing (2)
An alternative method of making WM5 keep the original .CAB file around after installing the application is by adding the "/nodelete" option to the Windows CE loader:
HKCR\cabfile\Shell\open\command = 'wceload.exe "%1" /nodelete' (REG_SZ string, no quotes)

Make WM5 prompt before overwriting an existing installation
If you wish to make WM5 prompt you before overwriting an existing installation, set:
HKLM\Software\apps\Microsoft Application Installer\fAskOptions = 1 (DWORD decimal)

To disable again:
HKLM\Software\apps\Microsoft Application Installer\fAskOptions = 0 (DWORD decimal) 

Improve Sound Quality of Speaker Phone
You might have observed that when you turn on speaker while during a call, the other person has complained of too much disturbance on the line and can hear more of static then your voice. Here's a fix to improve mic sensitivity:
HKLM\Software\HTC\AUDIOGAIN(x)\RECEIVE_UPLINK_VOLUME = CC (DWORD hexadecimal)
HKLM\Software\HTC\AUDIOGAIN(x)\EARPHONE_UPLINK_VOLUME = CC (DWORD hexadecimal)

where (x) = none, 0, 1, 2

Disable the security warning when installing non-certified application
To disable the security warning when installing a non-certfied application, set:
HKLM\Security\Policies\Policies\0000101a = 1 (DWORD decimal)

To restore the warnings:
HKLM\Security\Policies\Policies\0000101a = 0 (DWORD decimal)

Note that this makes it easier for any malware to install itself