You will and should not have a problem at all.
If you have your new rig all built up and working without a HDD, then, all you need to do is connect this Win 7 HDD to the SATA_1 connector on the Mobo, disconnect all the other drives except the ODD with your Win 7 Disc at arms lenght from you, just in case we need it.
Boot the rig straight into BIOS.
Set up everything like you need it, disable all other boot devices and make the Win7 the One and Only Primary Boot Device.
No Booting fro others, no usb boot, no boot from LAN etc etc.
Save exit and get into Safe Mode immediately.
Once in safe mode , remove old unnecessary drivers of the old mobo and software, lan chips and software.
Basically, remove everything that concerns the older mobo and gpu chipsets...
Reboot into safe mode a few times if necessary. How will you know it's necessary? well in safe mode windows will setup default drivers for the new architecture and components of the new mobo. This might take a few reboots as critical components need to be reconfigured by the OS. Also make sure that the RAM and processor are correctly recognized in the OS in safe mode.
After a few reboots and you feel that the rig is not doing anything new when it boots into safe mode, you can, reboot into normal mode.
Then install the necessary drivers either from the Mobo driver disc or the Windows Update site. You'll not have a problem.
I have been through a dozen rigs in the past 4 years and am still using the same HDD with the same OS that I installed 4 years ago, been thru AMD boards, changed over to Intel Boards, changed complete generations of CPUs and GPUs both Nvidia and ATI back and forth, and have not a single issue in terms of compatibility or speed every......