This where my lack of computer prowess gets me into to trouble. How do I make sure I've done this?
there are multiple ways to do it.
the bitcoin-qt client includes a feature that will allow you to encrypt it, however, that is probably the one you are already using that requires a download of the full blockchain.
you can also create a TrueCrypt container and store your wallet file in there. you really need to do your research in order to do this properly. go ask questions on reddit.com/r/bitcoin and reddit.com/r/bitcoinbeginners
keep this in mind: it may seem difficult to do all this now. and I sympathize. but understand that this is still a very new and developing technology. the infrastructure is getting built from the ground up. it will get easier to use. but right now we are in the innovator/early adopter stage. it's like the internet in the early 90's. sure, it existed, but it was difficult to get onto, required expensive hardware and specialized knowledge. but fast forward a few years, and it got much easier.
so be patient. you are an early adopter.
This post was edited on 11/8 at 11:52 am