I tried installing Vista Basic on a socket A motherboard with 768 megs of memory and 64 megs of that shared to video. Said it wouldn't install to a computer without ACPI. The motherboard has an AMI bios and does have ACPI capability. I had installed XP Pro on it though with that option turned off. So, I turn it on and still same error msg. Discover NT system needs a reinstall if you switch to ACPI power system control, can't just do a "repair", so reinstalled XP Pro over itself with ACPI enabled in the bios, which I'd also updated to the last available in 2003. XP still showed "Standard PC" in Device Manager under computer type, instead of ACPI enabled. Vista again failed to install on a "non ACPI" computer. Vista Basic won't directly upgrade XP Pro anyway, but I had the files loaded to hard drive in separate NTFS partition where I was also going to load it.
It may work on my socket 754 motherboard in other computer, not tried that one yet. I didn't want it on my newer main computer, not yet at least, wanted to test it out first on the other. If I find a work around I'll let you know. As for now, I'd suggest anyone with a socket A motherboard seriously consider NOT upgrading to Vista.
Oh,I also ran the compatibility guide and it claims it can't even run on a motherboard using the Sis 730 chipset, which is on this motherboard.
My advice? Probably better to wait till you buy a newer computer with Vista already on it and continue happily using one of the XP or Win2K versions on your older computer. As for me, although I have XP Pro, I've never really migrated over to it and continue mostly with win98se.
I tried the latest Live CD version of Knoppix, (version 5) and it worked great on both my computers, worth the download, or as I did, order a nicely labeled CD from Ebay vendor cheaply.