opened suspicious file for fun!... need help!

as the subject says, in a moment of idiocy I opened a file that appeared on my computer. now after 2 hours I've been searching and deleting and using scanners and have only a couple problems left! :).... :(....

so my problem is I cant change my wallpaper from a solid color. basically all the options on the desktop tab are greyed out and I cant even change it to the default wallpapers.

any idea how I could fix this?

sincerely,
Anonymous