If you're somewhat tech savvy, you may periodically look into the long list of processes that is running on your Windows PC. Google them by their "image name" or the name of the executable that's running and you often can find entries in windows process databases like this one, this one, this one, this one, etc. that describe the process as

   It is a legitimate program, but it isn't required.

After receiving my replacement eo from TabletKiosk recently to correct an issue with the usability of the TouchStyk I found that it had a whole bunch of processes running that I didn't recognize. One of them, igfxpers.exe, was described as "legitimate, but not required." So in an effort to reclaim resources that "unnecessary" background programs are using, I removed the string entry for it it from my registry's

   \HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

key without much thought. Only after about half a day, I discovered that it really was doing something useful and should be running.

I run my eo most of the time at a scaled 1024x600 display resolution. When you do this, the desktop resolution is set to 1024x600 and the touch screen display is told, somehow, to scale all rendering as well as all touch input. If you take a fresh-from-the-vendor UMPC that uses Intel's 915GMS video chipset and is running at a scaled resolution and shut it down or standby/hibernate it, you might notice that during the shutdown process, the display resolution drops back down to the screen's native resolution of 800x480 (that's native for the 2006-era UMPCs with 7 inch touch screens). When you restart the UMPC, the screen will be in the 800x480 resolution and you will have to adjust the display back up to the scaled resolution. Apparently UMPCs, or maybe it's just the eo i72xx series UMPCs can't remember the last used display resolution and restart with that setting.

Well, if you kill the igfxpers.exe process and remove it from your registry's ...\Run key, the automatic dropping of the display resolution does not happen as the UMPC shuts down. What you will find when you restart is that when you touch the screen anywhere but in the top left corner, the mouse moves to the right and below where you touch.

This is because the touch screen is showing a native 800x480 pixels of resolution, but the desktop/login screen size is larger. You effectively have a portal view into the unscaled desktop/login screen and have to pan around until you readjust the display scale settings.

Here's an depiction of what I'm describing (not to scale):

For example, if you touch the screen at the native position of [100,100] and your display resolution is 1024x600, then the touch screen is scaling the touch position to [128,125] (math explained: 100*ScaledWidth/NativeWidth => 100*1024/800 = 128, and 100*ScaledHeight/NativeHeight => 100*600/480 = 125).

When this happens it's REALLY hard to enter a password via the touch screen. You have to resort to using your UMPCs mouse stick or joypad and the mouse buttons to enter your password on the on screen keyboard or hook up a USB keyboard to enter your password and then readjust your display resolution after getting back into Windows.

Incidentally, if your system crashes or otherwise suffers an unclean power down and the screen resolution isn't dropped, you will see this same effect.

Summary

Don't always trust the "legitimate, but not required" diagnoses in those process databases. I don't know what else igfxpers.exe might do, but it is definitely important if you run your Intel 915 video based UMPC at a scaled display resolution.

And if you ever do disable one of these mysterious looking processes, keep a record that you did it. I got lucky and discovered the side effect pretty quickly. Had it been a week or so, I might not have correlated the removal of igfxpers.exe from the registry and the symptom I was seeing.