On Steam, I uninstalled TF2. A while later, I reinstalled it. However, when it finished, it keeps validating the game over and over again. I've tried many things; reinstalling it countless times, moving files, etc. and what I've noticed is that it does not do anything to my files when it installs (at least, to my knowledge) but it isn't detecting the files and still trying to reinstall. Is there any way to fix this?
This could be an issue with Steams permissions to access the folder, if you have it installed in a different location or have a windows link junction. But it can also be a mod you may have installed in the past.
Try fully deleting the folder for TF2
C:\Steam\SteamApps\common\Team Fortress 2\
Then install it through steam and see if it works. When steam uninstalls a game it leaves behind config files, settings, and certain types of mods.
Before deleting, you should backup the game to save your configs and such to reuse later.