Curious question

[TheyCallMeScruffy]

So Im building a new computer and im just wondering if I would be able to put in my existing Hard Drive with games and some files on it into the new computer, as it would make my life easier. Also to note this hard drive does not have windows on it.

[Spotty]

Yep. Pretty much just plug and play.
For games such as games in a steam library, you may need to assign a steam library to that drive so Steam can detect the game files located on the drive. (Steam > Settings > Downloads > Steam Library Folders > Add Library Folder)
You'll also need to instruct other platforms like uPlay and Origin where the game installs are located.