Delete save files

[Son of Gondor]

I was playing borderlands on my computer and then was playing on a friends computer for a while. The only side affect is that my save files were overwritten by his (only on this game) and now I can not access my save files. When I try to play the game it says I am playing as him and not me. I dont care if I have to start over but I want it to say that I am the one playing and not him. Any help? Is there a way to erase all information on the game?

[Bacchus]

My Documents\My Games\Borderlands\SaveData.
Disable Steam cloud.This is what overwriting your saves.