The usual method for accomplishing this does not work on the Infuse (i.e., there is no "bootanimation.zip" file). Here is a way of replacing it with the stock splash screen from the Samsung Galaxy S, of which the Infuse is a close family member... or at least a distant cousin lol! You'll need to be rooted to follow these instructions.
Download the replacement animation file, http://rapidshare.com/files/405635988/bootsamsung.qmg
Navigate to: /system/media and replace the exisiting bootsamsung.qmg file with the one you downloaded.
If you want to keep the original, rename it first before moving the ,qmg file there (e.g., bootsamsung.qmg.bak).
CHMOD the new file to 644 (same as the original)
Reboot and enjoy!
I have no way of verifying, but there might be a slight battery drain improvement with this mod, since the Galaxy S animation has a black background, versus the solid bright white of the AT&T splash screen.
If you just want to eliminate
the AT&T screen withoiut replacing it with something else, simply delete or rename the original bootsamsung.qmg file. However, if you do this, all you'll see is a blank black screen after the SAMSUNG logo extinguishes.
Now... if someone could just come up with an editor that could handle the proprietary .qmg file format, we could make our own animation screens!