Can I install unsigned Windows drivers to work without test mode or disabling driver signing and without buying a code signing certificate?

Can I sign drivers with a "self-signed" certificate, to work just with this PC, of course, and not have to use DDISABLE_INTEGRITY_CHECKS, TESTSIGNING or Test Mode?

Many modded drivers for legacy devices (e.g., ppjoy) are unsigned don't work in x64 Windows Vista, Windows 7 or Windows 8.

If this is possible, how?