The Classics came in a few different orientations:
* a thin 80 GB
* a thick 160 GB
* a thin 120 GB
* a thin 160 GB
Having that said, you can upgrade your iPod with a [product|130023|thin 160 GB hard drive] without changing any other parts. If you choose to go the thick 160 GB route, you will need to replace the following parts as well:
* [product|130014|rear panel]
* [product|130013|headphone jack]
* [product|130015|rubber bumpers]
* [product|130021|battery]
* [product|130016|hard drive cable]
I hope this helps!