When will the misery end? Initially, I only bought 2GB of memory for my x64 workstation. But I intended to add two more from day one, and today was the day - two additional Kingston KVR400X64C3A/1G DDR-400 modules were delivered to my doorstep. So in theory 4 modules would yield 4GB of memory.
Not so fast, Buster. Exactly. After finding out the hard way (blue screen and various other sorts of lock-ups), it looks suspiciously like the ASUS A8N-SLI Premium does not like four DDR-400 modules! (the ValueRAM site hints at this, and there are discussion threads too) that pretty much takes the biscuit.
Is there anything working on Windows XP Pro x64? I think not. Point in case: I just tried to install the Intelli* software for my Microsoft Laser Desktop 6000:

Now come on. This is Intelli* v5.4, a version that is newer than anything to be found on MS' download servers (where you won't find x64 versions either).
Windows XP x64 at this point in time is only for people who are willing to put up with below-par driver and application support. This experience almost comes close to Vista Beta 1...
Update Turns out I was one day too early. The new version 5.5 can be downloaded now, and it supports 64 Bit (IntelliPoint 5.5 x64, IntelliType 5.5 x64 [one download for x86 and x64]).