Best Way To Reload/Transfer W-7

New kid on the block here. I have an HP dc7900 running W-7 home and have my own W-7 Home 64bit disk. I'm upgrading to a HP dc8300 i5 with W-10. These usdt's have one hd that is 500gb. I have an 80 gb drive attached by usb that is my back up. I would like to load W-7 onto that one and put the 500gb in the usb holder and plug that into the the newer dc8300. Then I can go through get all the files I want to keep, format it and use it for my back up. Then put the 80gb in the dc7900 with the W-7 on it and use the W-7 activation code on the computer. I tried installing to the usb connected 80 gb drive but it wouldn't work. What's the easiest way to accomplish this being I am a novice at this..Thanks. GBY

Welcome to the forum. It's not clear what you want to do. You want to copy your data from the old PC to the new one how much data is there? You can't copy programme to the new PC. If you have the backup disk can't you copy files off that to the new PC? If you try and copy files files off the old Windows you may not a problem with permission

I just formatted the 80gb drive and want to put it in the my dc7900 with a fresh install of W7 that it came with. It is still attached to the computer by usb. I was hoping to load it via usb but it won't work. I was just wondering if there was any other options short of taking the 500gb drive out and putting the 80 gb in and proceeding from there. Thanks.

Do you want to do a clean install or use the one you have? Subject to disk usage you can clone you 500 drive to the 80 if the 500 c drive is less than 80 gig you can then put in the pc and it should work. To do a clean install you remove the old drive and put the drive in on its own then boot DVD and install

The old dc7900 has a LGA775 CPU.
The new dc8300 has a 1155 CPU that has completely different drivers.

Does the dc7900 or the dc8300 has the COA striker with win 7 key on it?
Is it for Win 7 Home premium or Home basic?

My suggestion is to do a clean install using the COA key to activate.
Clean Install Windows 7 - Windows 7 Help Forums

Yes I wanted to do a clean install on the 80gb drive for the 7900. I thought I could do it ahead of time via usb till the 8300 gets here. The 7900 has the W7 home coa. Thanks. GBY

Is win 7 key on the COA for Win 7 Home premium or Home basic?

Do you have your data backed up on another disk?
If you do, the best way is to do a Factory Recover on the original disk. Factory Restore will format the C: drive (that is why you need the backup on another disk) and reinstall Windows as it came from HP.
HP PCs - Performing an HP System Recovery (Windows 7) | HP® Customer Support
As factory recover restores a disk image, it has to be to the original disk.
Then with Macrium Software | Macrium Reflect Free clone the disk to the 80G disk.

It says windows home premium. No back up since I formatted the 80gb drive that is connected to the usb. The 500gb disk with the factory recover will be formatted and replace the 80 gb drive in usb holder for the W10 computer back up. The 80 gb drive with the fresh w-7for the dc7900 USFF will go on e-bay buy it now for $40 pluh ship cost. Thanks. Gby