I have my I-tunes library on my hard drive. Do I also have to keep them in my library on my Ipod or can I delete them without messing up my playlists?

Deleting the contents of your iPod shouldn't affect your library, unless you actively edit a playlist and that is synced back to the library. Ideally you would have a backup of your iTunes library on a second drive for security. See Backup your iTunes for Windows library with SyncToy for a suggested approach.

tt2

See Sync your iPhone, iPad, or iPod using iTunes on your computer - Apple Support. My opinion is that a little effort setting up one or two playlists to sync to your device makes it much easier to manage in future. Should you ever need to restore the device you'll already have a selection ready to restore to it. If you manually manage it you have to choose everything again.

tt2

I am a little confused as to why you want to delete the Library on your iPod. What is it that you are trying to do? As turingtest2 said, deleting the library on your iPod shouldn't effect the iTunes Music Library on your computer, and you can reload them on your iPod if you wipe it. Doing it the other way around is a different story.

To be honest, I don't know if deleting songs from your iPod will remove them from the playlists stored there. But as long as they exist in iTunes, you should be able to add them back.

If you want to keep only part of your iTunes library on your iPod to save space, in iTunes, go to Edit, Preferences, Devices, and check the box next to "Prevent iPods, iPhones, and iPads from syncing automatically". With your iPod connected, click on the iPod's icon in the top of the left column, just under the Account tab. In the Options window, check the box next to "Manually manage music and videos".

Now you can add only the Playlists or Music you want to your iPod but keep your entire library in iTunes. Be sure to back up your Library somewhere else as well 😉.

You don't have to sync everything to your device. Syncing with one or more selected playlists is an effective way to limit and control what you include.

tt2