This tutorial will demonstrate how to properly package and archive your mod.
Use Windows Explorer (located in Start, All Programs, Accessories)
Navigate on the left-side to C: and create a folder by right-clicking on an empty area on the right-side. A popup window will display, select New, Folder and then type MyMod and press ENTER. Press ENTER again and it will take you into that folder which should now read on the top address bar as C:\MyMod
Now, find and copy the .esp into this folder.
Find and copy the meshes and textures folders into this location as well (but make sure it is just your meshes and textures related to this mod).
When finished, your folder structure will look similar to this:
If you're using the 7-zip archiver (recommended, www.7-zip.org), go back into the root of the folder so that the address bar once again shows C:\MyMod and then select all the files (.esp & .txt) and folders (meshes & textures) and right-click on them. A popup window will display, choose 7-zip, Add to Archive. Set the following options and click OK:
Archive: MyMod (it defaults to the name of the directory)
Archive format: 7z
Compression level: Maximum
Compression method: LZMA
Dictionary size: 16 MB
Word size: 64 Check: Create Solid archive
Update mod: Add and replace files Uncheck: Create SFX archive
Password: [empty] Uncheck: Show Password Uncheck: Encrypt file names
Split to volumes, bytes: [empty]
After it creates MyMod.7z, double-click on this file and it will open up in 7-Zip manager and you can see the folder structure is how it should be if extracted to Oblivion's Data folder.