For Windows XP Tablet 2005
1) Removes tablet icon on taskbar (the one to the right of start menu button)
regsvr32 /u "c:\program files\common files\microsoft shared\ink\tipband.dll"
2) Removes Virtual Keyboard on login/logon (pointless if you use omnipass or you rather input it another way) It also have the sideaffect of removing keyboardsurrogate.exe which saves you about 8M memory.
regsvr32 /u "C:\Program Files\Common Files\Microsoft Shared\Ink\loginkey.dll"
3) Disable automatic updates under services (do not set to manual) will save you around 40M from 2 20M running services. If you want to run microsoft update (also known as the older windows update) than you have to set the service to automatic. Disable again when you install your updates.
4) Removal of omnipass 5 can free 40M of memory. If you don't need it that is. An excellent alternative is to use the asus fingerprint software... It actually works on the u810 and supports smartcards.
5) Disable last accessed timestamp. I generally never bothered since sata drives came out, unless you have a great deal of file monitoring tools like virus scanner, spyware detection. Even still it may be quite unnoticable because you are running virus scanner(S), spyware detectors... however u810 comes with a 1.8 inch drive running at around 4200rpm (most common laptops run 5400rpm) it will make a large difference. Don't run this if you plan to run defrag often (like more than once every 3 months...) or do some file monitoring for debugging purposes... Enable it by typing the following command either in run command or command prompt
FSUTIL behavior set disablelastaccess 1
6) Do not set power management to max battery. The reason is the power management setttings are set to degrade cpu processes (slow down your computer) for very little gain in battery life. More info here. I set mines to Portable/Laptop.
7) tabbtnu.exe is the icon on the notification area (Next to the clock). You can hide it by customizing the hide inactive icons in the taskbar and start menu properties. There also appears to be a program to remove this from your taskbar but since the source code is not released I will not mention it here.
8) Windows power management override the BIOS speedstep settings for the u810 (I believe that to be true). As stated above, setting power management at Portable/Laptop is adaptive and reduce usage to 598 MHz (You can check this in System Properties - General). I like this setting but setting powercfg.exe for dc to constant the cpu goes down to 448 MHz.
Happily running my u810 xp tablet 2005 sp3 at only ~310MB.