I'm curious as to what would stop working if I disable all the administrative shares on a Windows 7 machine that is not joined to a domain. Some of the KBs at Microsoft outline a host of problems that could happen if you were to do this on a domain controller, but clearly those don't apply here.
Nothing would happen, and your system would infact be more secure then having sharing enabled. I personally run an up-to-date Windows XP SP3 machine without any network services enabled, sharing included, and have experienced no side effects. While YMMV, this does infact apply to computers only connected to a domain (mostly used by corporations who keep a distributed group policy and enforce it across a common domain).
For additional security, you may want to disable unused connection protocols, which can be done by changing your network adapter settings, and unchecking the unused items (e.g. "Client for Microsoft Networks" or "File and Printer Sharing for Microsoft Networks"). The only reason I recommend that you disable the unused features is that leaving them enabled without any purpose is just one more risk of a security flaw in my opinion.