The following commands can be ran from the command prompt (ran as admistrator) to disable the driver sign checks in Windows 7.
You need to restart the computer before the changes work.
bcdedit.exe -set loadoptions DDISABLE_INTEGRITY_CHECKS bcdedit.exe -set TESTSIGNING ON
To return it to normal, run the commands:
bcdedit.exe -set loadoptions ENABLE_INTEGRITY_CHECKS bcdedit.exe -set TESTSIGNING OFF