Hello. Uh... I used to maintain computers in internet cafes. So yeah, there were many complains about the patching takes too long and etc because of DeepFreeze.
Now, I have researched a complete alternative to deepfreeze. Why? The technique is to exclude some folders that should be "writable" than "unwritable".
There are two of them and purely tested on various of timers (if timer was necessary. If standalones... it still works).
Shadow Defender (shadowdefender.com) - Shadow Defender has a very simple interface and programming. You can simply hide the icon and everything else so no one will notice that it is frozen or should i say... "Shadow mode". Every restart, it will set everything back to default. But regarding on settings like you excluded the games and the temp folders including My Documents for the save games... It will change but system files will remain unchanged. Reliable of course. Works on Vista and Windows 7 too. Works on Cafezee, Cafe Manila, and CafeSuite too.
Fortress Grand Clean Slate - Clean Slate is heavy in its settings. This is used if you own a regular internet cafe that doesn't have games at all. But very reliable and will not be much affected by viruses either with or without an anti-virus. But, some timers like Cafe Manila is much affected for the communications between client and server.