Installation goes well, then says it was unsuccessful

Hi,

I ran the vista advisor which said my computer would run Vista (as it did
with previous builds), but when I try and install the public beta, all goes
well and it restarts after completing installation, but then when it goes to
boot into Vista, it states that "the installation was unsuccessful, restoring
previous desktop"

I don't understand why it does this as the advisor said everything was ok,
and it should run on my computer. I really want it to work as I love the
look and feel of Vista.

Can anyone help? Thanks. Nathan.