Yes, you can. If you have at least 4 Gb of RAM. If you have less than 4 Gb there is no point for you install x64.
Yes, you can.
You should install it after Windows successfully boots.
Yes, you can.
Unless the new motherboard is the same chipset/model as the old one, Windows will not be able to boot up. The Windows HAL [Hardware Abstraction Layer] must be reconfigured to use your new motherboard. First back up all of your data! Afterwards, try running a windows repair using your Windows install disk. If this does not correct the problem, you will need to do a fresh install of Windows.
yes. yes.
Windows Vista Ultimate
Ultimate and Enterprise
There is no 128-bit edition of Windows.
The amount and configuration of memory is dependent not on Windows XP, but on the motherboard / chipset.
two
Yes, if you have the driver to install it.
Windows xp does not have native support for SATA interface (except SP3). You have to download SATA interface driver from the motherboard/computer website and use F6 installation procedure.
You have to check the motherboard manufacture website for drivers compatible with Vista Home.