Any alternatives to deepfreeze?

Sandboxie is certainly a less draconian/restrictive approach, yet no less effective.

Sandboxie is freeware although the 'real fun' starts with the registered version, forcibly run programs sandboxed, create multiple sandboxes, etc. (and you may install Sandboxie on any computer you own with one license).

I use both Sandboxie and Deep Freeze quite frequently, and they're both excellent solutions. Sandboxie does not support Windows x64, Deep Freeze does.

Returnil Virtual System 2010 (a combination of anti-virus and virtualization software) is another free (for personal use) alternative to DeepFreeze. (works with ALL Windows versions since XP, x86 & x64)

Horizon DataSys offer a variety of similar programs, such as Drive Vaccine (Automated PC Restore), RollBack RX and Executable Lockdown.

And speaking of Horizon, they bought a very interesting product (first they crippled it and then killed it altogether): with First Defense ISR you could take system snapshots (akin to snapshots of a VM) and boot to any of them. Any snapshot could be used as a live system or could be reverted to any previous snapshot state ... like keeping a jukebox of system drives and being able to choose any of them from a preboot menu.

BufferZone (pretty much like ShadowUser) creates an isolated zone on your PC, which separates your operating system and confidential data from unknown programs.

Having said all that, only Deep Freeze and Drive Vaccine (and indeed the demised FDISR) truly lock down the system to the very last byte. All other products are using virtualization, one way or other.

Two great alternatives are Clean State and Smart Restart. Both work in similar ways, with a few minor differences:

You may also want to consider running questionable applications in a virtual machine. You can take a snapshot once it's configured the way you want it, run any questionable application(s), then restore it back to a previous snapshot if anything goes wrong.

Deep Freeze and SteadyState by Microsoft are basic restore on reboot solutions. This means that users can do anything on the machines and then on every restart the workstations roll-back to a previous baseline setting.

I think that the best alternative that provides this basic feature plus some additional security would be Goback (now discontinued) and Drive Vaccine. The schools that I work with use Drive Vaccine to automatically restore their PCs on every start up and some labs set Drive Vaccine to restore at the end of every day.