There is no way to permanently disable the driver signing requirement on 64-bit versions of Vista or 7 through the registry or other simple settings. You must disable it each time you boot.
Some feel that it is an attack on free software. Certainly it makes it much harder. There used to be a signed driver whos only purpose was to load unsigned drivers, but Microsoft revoked its certificate under the plausible excuse that is decreased security (after all, malware could simply ship with that signed driver.) I recall the revocation of that certificate broke the popular Daemon Tools CD/DVD emulator.
More on the topic of the OP, however, I question the need to IN/OUT. If a userland application needs direct access to the hardware then its doing it wrong. A stable multitasking OS requires a layer of abstraction to prevent userland applications from arbitrarily messing around with the hardware. If this is a one-off operation, then provide a bootable disk image. If you need to do it often then provide a driver. A certificate can be picked up for under $100/year. Not cheap, but not going to break you either. If its for free software.. a few "donations" is all you would need to pay for it.
