As for the firewall, just use the Windows one. It works fine.
But, for your other answer-- if you can get into Windows, click on Start , then Run, and type in MSCONFIG. On the BOOT.INI tab, there's an option to click "SAFEBOOT". Check that, hit OK, and reboot. Your machine will automatically boot into Safe Mode. Once you're done doing what you need to do, just go back into MSCONFIG, uncheck SAFEBOOT in BOOT.INI, hit OK, and you'll reboot back into Normal Mode.