The thing is that I could play with any fullscreen mode without any type of stuttering prior to the 1.4 update. That's really the only software change that my machine's experienced lately.
It takes 0.2 second to tray down, 0.5 second to tray up. And I am pretty sure I don't have that 'microstuttering' in my gameplay.
Here's my setting layout:
Disable Aero Desktop: checked
Disable Driver Overrides: checked
Fullscreen mode: standard
Streaming memory: max
You choose: freezing and quick-switching or smooth gameplay and a bit slower traying down. I personally haven't found any configuration which would let me play smoothly and have instant tabbing.
Your config file might be corrupted. I had a similar problem, where my binds were somehow double and it didn't want to save anything. You could try checking for such errors or try installing a fresh MTA build.
Looks like the problem is caused by the operating system. The error message says that it couldn't find some 64bit >> 32 bit translating stuff, but windows XP wasn't even supported to have a 64-bit version.