Grey Screen on Starup!!!

So what I was doing was coping over my old hard drive to a brand new and bigger hard drive which I had partioned and formated already. I was using Norton Ghost 15 to do this, the procces took about 2 hrs. and 30 mins and when it was done I checked to make sure it had copied over correctly and as far as I could see it had.

But when I powered up my PC it started and went through the usual processes the spining glowing balls with starting windows underneath it, spining blue circle with welcome underneath it. But after the welcome loading circle is gone it comes up with another loading screen saying preparing desktop, this takes about five minutes and after it's done it comes up with a grey screen and in the bottom right coner it has this in this layout:

Windows 7
Build 7600
This copy of Windows is not genuine

I have tried restarting it over and over again, I have tried the Windows Repair disc which found nothing needing fixing and I have tried staring it in safe mode with no effect. I have looked around and can not find anything similar problem to this so I am hoping that someone knows how to fix it here. :)

Computer Specs.
Windows 7 64 Bit
Intel Pentium D 3.0Ghz
Nvidia Geforce 8800GT
2 GB RAM

Just ask if you need any more information.

Thanks for the quick reply but I do not have any access to my computer (I am on a friends right now) without changing the new hard drive for the old one.

Managed to fix it!!!!! what you have to do is go into safe mode with command promt and keep pressing ctrl-alt-delete until it comes up with a list of option which are shut down pc, log off etc. but you need to click on start task manager then you click on the file menu on task manager and click new task and type in "regedit.exe" (without inverted commas) and tick the box with run with administritive priveleges then you follow these steps: -

1. Go to the following registry key - HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
2. Then find the drive letter you want to change, look for "\DosDevices\C:" right click on this and click rename and change it to another spare letter key Z etc.
3. Then find the drive letter the new hard drive is under (in may case) "\DosDevices\:F" then right click and press rename and change the drive letter from F to C
4. Quit Regedit
5. Restart your computer

If you followed the steps above it should boot up as normal and it will work fine.