[Dwragon]

deleting everything in your Steam/steamapps/username/team fortress 2 folder.

Its fine as long as you use the steam cloud, backup/no autoexec file and you don't have any custom maps/sounds/mods. What the game does is cache sprays and avatars. If you play a lot, this can build-up overtime but the worse I can see it do it add more fragmentation.

So you can do that, defrag your cache files in steam and do a HD defrag. Going a bit further, hopefully you have at least a 7200 rpm hard drive but if you want bump up to a 10k or even an SSD. Lastly you can overclock/get a higher clocked cpu. HTH.