I cannot guarantee that Pre-RC1 (beta 3) will solve your issues.

In fact, I wouldn't recommend anyone use pre-retail builds of OS at all, unless they have sufficient technical expertise to solve the problems they encounter themselves. You wont find anyone who can provide good tech support on Vista at this stage. There's a reason why no software or even drivers are supported in Vista yet. I would certainly in no way recommend installing one beta of Vista on top of another.

You're much better off reinstalling Windows XP.