Help with logon background changer.

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C#

Windows

Win7

i need some help. i am trying to make a logon background changer for windows 7 using vs2008
i found a similar project here, but it was done in VB, while i would like it in C#.net.

now, there are a few ways to go about this.
The way it was done in the vb project was to first confirm the OS version, check for the 'oobe/info/background' folder and create it if necessary,
show the user a dialog box with buttons to browse for an image, use the bitmap object to format the image to a jpg, rename it to 'backgroundDefault.jpg' and copy it to 'oobe\info\background'. also, check the registry key to allow win7 to use a custom logon background.

now, whenever a user wants to change the logon screen, he runs the prog, selects an image and hits 'apply' button and the image is set as logon background. Of course, the image the user selects is restricted to a fixed max size only.

another way is what is done by logon screen rotator by Luke Payne.
here, the app allows the user to select multiple images, of multiple formats namely jpg, jpeg, bmp and png files...without restricting file-size.
then, it allows the user to set a schedule to when the logon background has to be changed, namely: once, at logon, at each computer lock and so on...
then the app randomly selects one among these selected images and uses it as the logon screen according to the set schedule.
i have used this app. but i couldn't figure out how it works coz, the logon background does change at each logon, but i couldn't fine any image files in the 'oobe\info\background' folder....

so how does this app make win7 load the custom logon background?

i think the list of user added images could be written with full path in an external XML\ini file so we could use a
multifile select dialogue box for this purpose.
the question is, how to circumvent the max file size check and the file format check employed by win7???

also, i need help on programatically setting up schedule tasks for this.

Of course, i can continue to use Luke's software, but i would like to learn how to make one .

Thanks.