In the folder C:\windows\resources\themes as boohbah suggested, you are to delete two items. One is the theme folder, and the other is the windows theme file, both for the theme you want to delete.
Why not simply delete them from the selection screen (the one you showed in your pic)?
Right click on the Theme you don't want anymore and click "Delete Theme"
That obviously doesn't work with the active theme, so if you want that gone make another one active first.
-DG
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David, as I have experienced, this action deletes the Windows theme file only, but not the folder that contains the visual style file, languages files, etc.
Archie, I must confess that I never checked if really all files are deleted by that method. The left overs don't really hurt me or my disk space So yeah in that case it's better to "pull the carped under window's feet" and delete those files in ..\Resources\. But make sure you delete the correct files! For inexperienced users my method is simply the safer one.
-DG
My Computer
Computer Manufacturer/Model Number
HP m8000n
OS
Windows 7 Ultimate x86
CPU
DualCore AMD Athlon 64 X2, 2600 MHz 5200+
Motherboard
Asus M2N68-LA (Narra)
Memory
Samsung 2GB DDR2
Graphics Card(s)
Onboard NVIDIA GeForce 6150SE nForce 430
Sound Card
Onboard nVIDIA nForce 6100-430 (MCP61P)
Monitor(s) Displays
Westinghouse 19" LED
Screen Resolution
1280x1024
Hard Drives
SATA II Seagate Barracuda 500GB
USB II WD Elements 500GB
USB II WD My Book 1TB
USB II WD My Book 2TB
You are absolutely right, my friend. Usually the theme files are tiny And leftovers dont hamper anything. moreover, if you delete wrong files, your installed themes will be in trouble.
So, rightclicking and deleting is not a bad option at all. But it doesnt delete it completely.