Sandboxie allows you to run your browser, or any other program, so that all changes that result from the usage are kept in a sandbox environment, which can then be deleted later.
What's new and changed in this version:
SANDBOXIE INTERNALS REDESIGNED IN VERSION 4
The 64-bit edition of Windows 8 introduces a new version of the Kernel Patch Protection (PatchGuard) component, which limits Sandboxie v3 in establishing some of the kernel hooks that it needs in order to fully supervise programs.
To ensure a high level of sandbox isolation on Windows 8 and future versions of Windows, and to mitigate the risk that a future update to Windows 7 will include the new PatchGuard, and break compatibility with Sandboxie, version 4 introduces a change in the way Sandboxie works under the hood.
In version 4, Sandboxie is designed to not rely on unofficial hooks into the kernel. (A few such hooks are still in use on Windows XP.) Instead, a program under the supervision of Sandboxie v4 runs with no permissions and cannot access or manipulate objects in the system outside the program's own memory. (This restricted security context can be seen by looking at a process in the sandbox using Process Explorer.)
Sandboxie 4 on 64-bit Windows removes the Experimental Protection feature, and no longer has to suggest use of Drop Rights option.
Minimum Windows Version
Features in the Windows kernel which guarantee that a program cannot improve its own set of permissions are only available starting with Windows XP SP 2, with additional security features in Windows Vista.
Sandboxie v4 officially supports Windows XP SP 3, Windows Vista with Service Pack 2, Windows 7 with Service Pack 1, and Windows 8. Other variants may or may not work at this time.
Please note that these changes do not mean that Sandboxie now supports Metro apps.
Beta version 4.01 is a major change, please expect that some things may break.