You can't do it through the folder view - it, the folder that opens up showing ipod files. You can't transfer music to the ipod that way, as iPods anre not drag n drop. You have to do it through the WMP library. Plug in ipod, open WMP and slick the sync tab. Then you should be viewing the ipod as the device. Click ALBUMS (or artits, songs whatever) on the tree on the left, under the word library.
Highlight what you want to copy to the ipod, for example, I will do everything by one artist. Then right click and select "ADD TO SYNC LIST"
Do this for everything yo uwant to copy, then on the right side (under the list of songs you have added the sync list just hit the SYNC button;
Let it do it's thing, when it's done you need to disconnect the ipod from the PC first - task bar by the clock, little green arrow thing, click once on it and you get a list open of devices connected. Click on the ipod entry and it will pop up a balloon to say it's safe to disconnect the ipod. Wait till ipod screen shows the menu (not the red cross circle) and then unplug it.
Sorted