Yes you can using a special installer file. See the instructions below.
(Note: This file does not work for LabQuest 3.)

1. Click to download the special update file Installed102Labs.lqu.
2. Copy the file to a clean USB flash drive or SD card.
3. Plug in the USB flash drive or SD card into your LabQuest.
4. Open the LabQuest System Information by tapping the Home Icon, selecting Control Panel (original LabQuest) or System (LabQuest 2), and then System Information.
5. On the Summary tab, tap Update LabQuest.
6. Tap on the USB drive or SD card icon near the top and highlight the LabQuest Library update file, Installed102Labs.lqu.
7. Tap Update to start the update. When prompted to install the update, tap Yes.
8. When the update is complete, close the System Information window.

This will add the default 102 labs back to your LabQuest. It will not remove other files you have added. To remove those files, see How do I reset the LabQuest 2 defaults when installing an update?.