Ahh I'm not too sure because I don't have my HDD partitioned

But... when you first install LW & go through the setup wizard certain folders are added to My Library by default - unless you choose not to add them ie Desktop & My Documents. Which is very different to LW 4.

In LW 5, go tools > options > My Library. There, you'll see which folders are added to My Library. If you want to remove certain folders, just click on the 'remove' link beside the folder & then click the ok button at the bottom of the page. The folders will be removed from your library but still saved as they were on your HDD.
On that same page in options, you can add other folders to your library (if you want) by clicking on the 'Add Folder' button & then browsing for the folder. Just remember to click 'ok' to save any changes.

Folders in My Library shouldn't be shared by default (ie not available for download) but just check your P2P Network (in LW's sidebar) to make sure.

Does that help?