Why does the most easy and straight solution go unthought of.... No need to patch WFP. No need to deal with .theme files. No need to replace files on I386. a. Using batch-file, delete %WinDir%\Web\Wallpaper\Bliss.bmp b. Then copy over your own BMP using copy commands in same batch-file! That's all! That's what I do, and it works perfectly. I am in a hurry as of now, but I'm sure the others here will be able to tell you how to do steps a & b unattended. Things to know: 1. Place your intended new wallpap in "$OEM$\$1\install\temp\Bliss.bmp" or wherever.... just ensure that your .CMD can access it. 2. The file delete+copy should happen at T-12 (cmdlines.txt stage). 3. Remember, remember, remember.... its a BMP to be replaced with another - don't use JPEG/GIF/PNG.