I used to forget about that particular limitation of RSA, too. I’ve made that mistake two or three times before I finally gave up and started remembering it.

Regarding the praticality of use against large files: instead of reading all of the data into memory, you could use a CryptoStream and “stream through it”. You provide it with the encryptor or decryptor creating from the Aes algorithm and it takes care of all the error-prone streaming and buffering operations.

If you can use .NET4 (maybe you can’t because your victims audience won’t have it installed), there’s a CopyTo method on the Stream class that simply pumps an entire stream to another, with a buffer size parameter. If you can’t you’ll have to do the pumping “by hand”.