"Old" hard drive in new build

Hey there guys. I recently just built my friend a system that we had been planning on for several months now. My friend was robbed last year and his laptop was stolen along with a lot of other things. I gave him my old Dell so he would have a computer, but he had to buy a new power supply and hard drive in order for it to function. I told him "Just save up some more money and we can buy the rest of the parts to make a totally new system that's way better." And so he did, which brings me to this topic of discussion.

Everything is built physically with zero issues. The only hitch I've come across during this process is throwing his hard drive in to this system. It's an entirely different hardware configuration, thus Windows refuses to boot. I could have sworn there was a way to get Windows to recognize the new hardware and boot up normally. Does it perhaps involve booting in safe mode and doing something within Windows? Or is there a utility in the BIOS I'm not aware of (I've searched through it a dozen times now) that allows me to do this?

I would rather not reformat the drive because he has data on there, and I don't really have any viable means of backing it all up efficiently. I only have a crappy, 16gb flash drive. That wouldwork, but it would be a stupid, lengthy process. I'm like 85% sure that there's a method out there that lets you avoid reformatting. I tried Googling it, but I kept getting poorly-written tutorials for installing hard drives in to a case, and installing an OS on a hard drive. I guess I just don't know how to word it properly so that Google actually knows what to look for.

 

Any help would be greatly appreciated. Let me know if you need any additional info, like hardware specs and such.

https://www.youtube.com/watch?v=aFJwiILbsdo

 

the setting up takes less than 2 minutes

http://www.mytechguide.org/10042/windows-7-service-pack-sp1-official-digitalriver-download/

download w7 legally from ms there. take me 3 mins to download

so total to create win install flashdrive its 5 mins

install windows but dont format. just cluck the drive then next all files will be moved to a folder at C:\Windows.old. then he will have all his files and a new install.

should take less than 1hr to complete

First try inserting the Windows Installation disk and do a "Repair Install"

Second - depending on just how different the hardware is you may HAVE to do a full reinstall - if thats the case and you really dont want to lose any data - plug the hdd into another computer as a second drive and copy everything before you do a reinstall

 

there may be other ways to do it but a repair install has always worked for me

Of course! I always forget about the damn Windows.old feature. Might as well just do that so I don't get any weird dirty driver shenanigans.

The old Dell is from 2006, so...yeah...

 

Anyway, thanks for the help fellas. It's appreciated.