Hello,
Sorry to hear.
Unfortunately, even if iTunes hadn't of updated your iPod and removed all the tracks on it, there would be no conventional way of transferring back your songs from your iPod to the PC anyway. It's not supported because of Digital Rights Management protection from copyright infringement. However there are applications which could have uploaded your tracks from the iPod to the PC - but all filenames would be generic and songs would be in an illogical order...
...iTunes couldn't find the files listed in the library on the PC's hard drive, and so erased all your tracks on your iPod when updating - because it was set to automatically update when connected. Unfortunately you needed to backup your music files prior to formatting the hard drive.
You could try to use a data recovery program and attempt to recover your music files (even though you've formatted the drive). The files are still there, but just flagged deleted. However, I can't guarantee that you'll recover all your music files (if any) because data may have been overwritten and used up by new software installations (such as re-installation of the OS). I can't name any freeware or shareware data recovery programs, but some do exist.