I deleted a batch of my videos that I didn't mean to!!! Is there any way to recover them?? (they were only on the hard drive, no memory card)

In this case you should try some video recovery software to rescue the lost videos from your hard disk ASAP(in case overwritten), here are some programs you may rely on. Both programs can also recover photos and music.

Photo Video Recovery (for Windows)
Mac Photo Video Recovery (for Mac OS X)

Note: Take the free trial first, and before your videos are recovered, do not attempt to save more files to the disk in case the original files(your deleted videos) are overwritten. Regards

Ok! That often depends on what have you done to this camcorder? Have you saved anything new on this camcorder?
In fact, the deleted videos on a camcorder are not actually erased as we normally think after the deletion process. They are still there and only become invisible. As long as you've not rewritten them, you always have chances to get them all back.
So, I hope you've not overwritten them all.
Here are my steps for you to get them all back:
Step1. Stop using this camcorder in case that any new file would rewrite your original videos.
Step2. Plunge this camcorder to your computer and prepare to restore your videos.
Step3. Download a camcorder recovery freeware to your computer and start to retrieve all your videos back:
http://www.freeware-fix.blogspot.com/2013/04/data-recovery.html
In fact, this freeware has ever successfully saved all the inaccessible data of my friend off from his camera. So, I believe it can also work successfully on your camcorder, too.
Simply read more information of this freeware here:
http://www.geeksdo.com/data-recovery/
Step4. Save and back up all the restored photos on a different memory card or drive in case of data recovery failure.
Note: Next time, you'd better never be so careless about your important videos and always remember to back them up on separate memory cards or drives in case of the similar data recovery problems.