Constant readers may recall my skiting earlier this year about the splendid new computer I assembled for myself over Christmas. Up to now, however, I haven't mentioned the sorry fact that the damn thing stopped working last month.

No, it wasn't Windows' fault - it was mine, for attempting to recycle the 500GB hard drive from my old computer And why not? It wasn't very old, but apparently it couldn't stand the gaff in the new box and failed.

So a new hard disk, then, 750GB with a SATA interface this time, bigger, faster and newer. And an opportunity to do a few things differently in the course of a complete re-installation of all software, particularly one thing: 64-bit Vista this time instead of 32-bit Vista before.

What's the difference? I note that both versions cost the same according to Microsoft New Zealand's website, $300 for Vista Business or $320 for the even nicer Vista Ultimate, so that doesn't matter.

Performance is another thing. Last century CPU and bus width was a clue to a small computer's power - I recall a snotty salesman in Tottenham Court Rd steering me away from a H-11 computer with a 16-bit LSI-11 CPU and suggesting I try an 8-bit Apple II or TRS-80 instead. Since then it's been a steady progression: when 16-bit computers are the norm, 32-bit computers are the high-power "workstations" that ordinary folk will never need; and now that 32-bit computers are the norm ...

But actually it isn't such a big deal - the Intel Dual and Quad Core CPUs that are the standard now run either 32 or 64-bit code with practically equal facility. The theoretical advantages of 64-bit are a larger memory address space and potentially more CPU instructions but that's up to the chip designer.

The larger address space may be important: 32-bit computers top out at 4GB RAM, an amount that seemed unimaginable a few years ago but which is not that special now. 64-bit computers top out at 1.84 x 10^19 bytes, and it'll be a few years before anyone slots that into a desktop PC, but being able to hold just about any conceivable database, picture, or even an entire movie or 20 in memory will be useful to some.

As for my practical experience: the alleged shortage of 64-bit Vista drivers hasn't bothered me at all - the only problem I've had has been that Adobe doesn't make a 64-bit version of Flash, which means the otherwise slightly more sprightly Windows Explorer 64-bit can't display the many websites that use Flash extensively. This is probably why Vista's 64-bit install also puts a copy of 32-bit Explorer on the hard disk.

Subjectively, 64-bit Windows Vista appears to be a little bit snappier but a lot of that could be the new hard disk. Nevertheless, I don't see any disadvantage to it and I'll be running 64-bit on all my computers in future. I may even go out and buy another 4GB of memory.