Help With Skinning

I am starting to model with gmod, so i am going to start out with skinning.
I have GCFScape, and when i extract the “citizen_sheet.vtf” source texture, to “C:\My Skins” folder, i get this error in the console thingy:

Extracting to C:\My Skins.
Error writing C:\My Skins\citizen_sheet.vtf (File contains no physical data to write.)

Help much appreciated.