Desktop Picture/Theme Issue

Hello,

I noticed recently that I am unable to change my desktop picture, I'm also unable to change the theme of my computer when trying to personalize it.

I've tried by right clicking the photo and selecting "Set as desktop background." I've also tried by clicking on the "Desktop Background" option and changing the photo in the Control Panel - Personalization section. Neither work. When I click on them, instead of changing the desktop image, nothing happens at all. There is no error message, so I don't know how to go about fixing it.

I appreciate any help given at all. Thanks for your time.

System Info:
Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Professional, Service Pack 1, 64 bit
Processor: AMD Phenom(tm) II P940 Quad-Core Processor, AMD64 Family 16 Model 5 Stepping 3
Processor Count: 4
RAM: 7926 Mb
Graphics Card: ATI Mobility Radeon HD 4250 Graphics, 256 Mb
Hard Drives: C: Total - 459230 MB, Free - 371339 MB; F: Total - 2035 MB, Free - 391 MB;
Motherboard: Hewlett-Packard, 142C
Antivirus: Norton 360 Premier Edition, Updated and Enabled