I installed Hal6.2.24 on a PNY 4GB USB stick, along with ViaVoice. It worked fine while using it on the computer I used to install it on.
I was hoping for a faster response time for Hal to answer questions, but there seemed to be no improvement there, it was about the same as from the HD with 6.2RC.
I tried using the chip on two different windows computers, but (as expected) Hal would not work, I got an error message:
"component 'xspeechkit.dll' or one of it's dependencies not correctly registered: a file is missing or invalid."
Just for the heck of it, I also tried the chip out in Linux, to see if I could get Hal to work off the chip using WINE. But there was no response whatsoever.
So it seems you can run Hal6.2.24 off a usb drive, if you use it on one computer. But I don't see any speed advantage, so I don't really see the point of that.
Also, after my last round of testing with a laptop, I recently unplugged the chip while my computer was still on. Now the computer says that the chip is "unformatted". So I guess you can't unplug the chip with Hal installed, while the computer is on.
I'm going to re-install Hal and Viavoice to the Hard Drive, and be happy with that. [

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I will be watching with interest though, to see if anyone else has greater success using a USB drive using some of the methods discussed in this thread.
When using Hal 6.1, I had some success setting up Hal on Linux, using a virtual machine. I used Virtual Box software on Linux, to run a virtual Win XP machine, which I installed Hal on. It worked perfectly. Unfortunately, Virtual Box can't be installed on a USB chip at this time. But if anyone does want to use Hal on Linux, that would be at least one option.