The problems seems to be with the copying of Acceleration to the new HD. I'm no tech guy, so I'm not sure, but did your sync program also copy the related registry entries? they often control piracy protection and the likes. Do you have other problems running acceleration or FSX?
My best advice is just start with a clean install. I did that when I transitioned from Vista to W7, and I had no problems whatsoever. It takes a lot of time, I know, but if you run a trouble free FSX, it was time well worth spending.
What you can try first, is insert the Acceleration DVD, and see if the 'repair' option works. If it does, try that. If not, I'd say clean install...

About the custom HUD, I installed one too (I think it'll be the same lol)
and had the same problem. This is caused by a CS gauge running in the background, doing the piracy checks. If you don't run it, the protection will activate, and your aircraft will be unusable.

To solve it, pay attention when you install the new HUD. there is a line in the original panel.cfg that's not there in the acceleration hornet panel.cfg (actually, several) those lines should be kept, or you will loose functionality, like animations panel and weapons panel, and of course the piracy protection kicking in.

If you solve your acceleration issues, and still need help getting the HUD to work, post here, and I'll see what I can do to help.

Lars