I am new to DNN and I am trying to learn how to create skins for DNN 5.0.  (Nothing fancy, would just like to be able to make a simple skin.)  I have bought a number of books but every sample skin code I find in books gives me an "Invalid File Extension" message (I assumed because the books are all 4.x versions of DNN). 

I thought the best approach would be to make some very minor changes to an existing 5.0 skin. I downloaded a free DNN 5.0 skin and unzipped it into a folder.  I then made a very minor change to the ascx file in Visual Studio 2008.  The skin I downloaded had a LeftPane and a ContentPane.  I made only one change.  I cloned the LeftPane and renamed it RightPane.

I then saved it back to the folder and rezipped the folder.  When I uploaded it to my portal on DNN, I get "Invalid File Extension" message and it willnot install.  I then tried the original unedited zip file and it worked fine.  I then tried unzipping the original skin folder and rezipping it WITHOUT MAKING ANY CHANGE.  Again I got the "Invalid File Extension" message.

Again I took the copy of the original zipped file I had downloaded and again that copy worked fine.  Does one have to do something special when zipping the files. Is it possible that there are compatibility issues among zip programs?  What zip programs work for sure? 

Has anyone else had similar problems and how did you resolve the problem?

Thanks in advance.

No, that is not it.  I zipped at the file level and have compared the contents of the new zipped file to the original zipped file.  Looking at the zip file contents, both have the same structure.  I use 7-Zip as my zip utility (but with the zip file extension) and I am wondering if that could be causing the problem.

I am also wondering if there is somethingin the structure of downloaded skin files that cause them to break if you modify one of the files.

All the file names match 100%.

I have tried both ways, including Send To ... Compressed Folder.  The thing I find strange is that when I do nothing but unzip the downloaded zip file and then simply rezip them (I am simply highlighting all the files in the unzipped folder and then selecting Send To ... Compressed Folder), when I try uploading and installing that copy of the zip file I get the invalid file extension warning, but when I upload and install the original file, it works fine.

When I compare the content of the two zip files, they have the same names, the same size and the same files inside.