Help: issues with Windows Vista Home Premium upgrade

Hi guys,
I'm experiencing some major problems with Windows Vista.
I bought an upgrade DVD, so, basically, I have 3 ways to install the new OS:
1) upgrading the existing Windows XP installation (the worst solution, in my
opinion), 2) running the upgrade DVD under the legacy OS (e.g. executing the
installation under Windows XP, but on a different partition), and 3) using
the Dailytech trick to run the installation off the upgrade DVD (first pass
without typing the product key, second pass by using the Windows provided
number).
I have 2 S-ATA disks, the first one containing the XP installation and
another data partition, and the second one that is destined to Vista (the two
disks are respectively disk 0 and disk 1 under the two OS's).
The problem is that I'm having strange issues when I try to install Windows
Vista, by both using method #2 and #3.
The process usually runs smooth until Windows copies and expands the files,
but the PC sometimes reboots during the completion and I have to select the
option to start Windows normally, because the system has been shut down badly.
Other times, the PC reboots before I see the screen where you type in your
user ID.
Some other times, the system goes to the desktop and the PC reboots during
the process of checking system's performance (in this case, I have to start
Windows normally and the OS asks me again to configure my account. After
that, Vista tries to ckeck system's performance once again).
I even received some BSOD's during the entire process, like e.g.
BAD_POOL_HEADER or 0x00000019 or 0x0000008E (one of these blue screens
pointed to a file called "fltmgr.sys").
I point out the HDD that I'm using for Vista is brand new and I tend to
believe it's not the culprit.
With some variations, these are the issues I'm experiencing and to make
things worst I have the problem that I usually need to make a second
installation after that; of course, the second run can completely screw up,
making me even more miserable.
I tried to disable all unnecessary peripherals, like the 1st LAN, integrated
audio, etc.
The funny thing is that, once the installation process is done, even if with
all of those issues, the OS runs fine and it does not return any errors.
The only problem, as far as I know, seems to be the installation in itself.
So, I ask you: did you have any particular issues?
What step did you take in order to upgrade your system?
Any suggestions would be greatly appreciated.
Regards.