Hmm, not sure exactly what's your problem. Maybe a cleare description of the problem will let other help you.

If Windows XP 64bits don't support a particular software, there is a high chance that software won't run in Windows Vista x64 as well.

Yes, it is stable enough that Microsoft will release the retail packs for Vista including SP1 as well. Just like what they used to offer in retail packs for Windows XP SP2.

There isn't a lot of native 64-bit device driver available for XP and Vista. Also Vista 64-bit enforced that all device driver must be signed otherwise it can't load. That's the challenge most user faced when trying to move up to Vista 64-bit.

Hmm, never heard of that. Do you have a link to site that state this is the case?

I only know Vista 64-bit had driver signing enforcement.

Thanx.

Did you reboot after installation of SP1? If after reboot and you still don't see the "Service Pack 1" in Computer->Properties, you might not have install it correctly.

If you are not using the RTM version of SP1, then you'll hit the expiry which cause BSOD as the pre-RTM version of SP1 expired on 30 June 2008.

If you have a licensed copy of 32-bit DVD for Visa, call Microsoft to request a copy for 64-bit. Otherwise, get a retail pack of Vista Ultimate.

Probably some Shell extension for recent items is broken. When you upgrade to SP2b, it fixes the extension so now everything is back to normal.