UPDATE: Unfortunately, for some reason the people at Redmond decided to remove this feature from Windows 7.

Zheng-a-boy had posted that Windows 7 will feature a that will allow admins sandbox user accounts on the  PC. Apparently, back then it was called PC Safeguard, it now has been renamed to Guest Mode. Essentially Guest Mode disallows users to save files to locked drives & undos any file saved or changes made by this account upon log off. The Guest user account is different from Guest Mode. In order to do this, you will need to create a Standard user account. Once done, follow the steps & screen shots:

1. Control Panel –> User Accounts and Family Safety –> User Accounts –> Manage another account –> Select the account you want to restrict

2. Click on Set up Guest Mode. Screen shot:

3. Turn on Guest Mode –> Apply

Notice that the user picture now changes something like this:

4. You should now see the Lock drives (Advanced) option enabled. Screen shot:

Clicking on it will show you a screen listing all hard-disk partitions with their current status of being locked or unlocked. Screen shot:

5. Selecting the partition gives two options, that of locking or unlocking the drive. Screen shot:

Upon choosing the drives you want the account to save files, you’re done.

NOTE: The saved files will deleted upon log off.

The user when (s)he logs on will be greeted with the following message, screen shot:

~Enjoy!