Using old SSD with OS on a new computer that already has an OS

[gmamafilms]

I'm building a new computer and I know that I can't use my old boot drive, but can I use that old drive(with Win 10 os) and still have it work the same on the new os?

 

[AniChatt]

Look your statement is not clear. It seems like you have a old ssd with installed windows and you want to use it in your new PC with Windows 10. You no need to buy another ssd if you don't want say extra space or performance. Just salvage the old SSD from old computer, install it in new PC then format it with windows 10 you will be good to go. Otherwise if you are planning to add a new ssd then use this old ssd for extra space in your pc and again format it to use it as a regular storage drive.