I've never tried, but I would think that Explorer would allow you to tranfer or copy if it recognizes your phone as a storage advice.
You need to know where iTunes stores your tunes. To open Explorer, the easiest way is hit the windows key on your keyboard, and while holding that, hit the "E" key.
Drill down to the file with your tunes. Select the ones you want to copy. To select multiples, you can hold the control button while left-clicking on the mouse. To select several in a row, just hold the shift button, click on the first of the list, then hit the down arrow to select more.
Right click the mouse over at least one of the files. Click "copy", then wait for Windows to copy the files.
Go to the directory for your phone...assuming you've hooked it up (say via USB), it will likely be something like the E drive or a higher letter if you have multiple optical drives and/or a card reader.
When you get the one for the phone, right click in the directory in the phone where you want the files to be copied to. Right click on that directory, then click on "paste". Windows should give you a progress bar that shows the files being copied.
If you wanted to transfer rather than copy, the process is somewhat similar. However, it's better to just copy and make sure the file transfer took, then go back and delete any files you didn't want to keep in iTunes.
