Retain physical side by side possession of both systems until successfully evolving your existing Windows install to your new system.
Is your version of Windows 32 or 64 bit?
Are you upgrading a 32bit version of Windows to a 64bit CPU?
32bit Windows accomodates the 64bit hardware space, cramming a 64bit version of windows to a 32bit CPU creates endless issues.
Download and INSTALL Minitool Partition Wizard 9, free and reliable for migrating/upgrading Windows across drives, do so now before opening either case
It's crucial Partitiwon Wizard is verified installed in your existing legacy drive.
MIGRATION PROCESS:
Retain possession of your existing working hard drive, your friend will have to wait for the moment.
Connect your existing drive to your newly upgraded motherboard.
Boot, be prepared for an interrupted boot process with "Startup repair" messages, as long as they don't become crashes or endlessly spinning overnight.
If your old system successfully boots to your new board, you're doing well, messages about missing drivers are expected and inconsequential for the moment. Ignore them for now since your existing build has evolved (upgraded to your new hardware).
Power down, connect your new target HDD alongside your upgraded drive, reboot.
Launch PW9, Wizard pull down menu / Migrate OS to SSD/HD Wizard
Selecting your existing disk for copy to your new target disk is too easy to blunder
the system will demand a reboot, do so and your disk copy will complete at the fastest pace possible
PW9 robustly adjusts the new drives BCD settings for novices uninterested in mundane drive geometry.
PW9 completes successfully, WILL DEMAND A RESTART.
DO SO, IT'S REQUIRED TO COMMIT CRITICAL CONFIGS AND IF PREVENTED / CAN RESULT IN TARGET DRIVE INSTABILITY OR BOOT ISSUES AND RESTARTING THE ENTIRE COPY PROCESS.
Reboot the system again, successfully to Windows, whether the system booted from the old or new target drive is irrelevant for the moment since the final PW9 commits were the objective.
Shut down windows, power down system.
Replace your older existing drive with your new target drive in the same cable slots/connectors.
Remove your older drive completely from the system, ensuring it isn't powering or booting your new box, set the disk aside.
power your new disk, with newly copied target drive in the old drives slot.
If boot to windows, you've succeeded, register it if you need to or start upgrading your device drivers.
complete your device driver installation process
Now, your old hard drive can be relinquished, reinserting into your system for a secure data wipe or rudimentary formatting can be accomplished with PW9 or various other utilities, how trustworthy is your friend determines whether you're comfortable turning over your existing data or prudently erase your drive before gifting.
Have a brandy and congratulate yourself.