SL install can't write files

During the install, an error box popped up and stated that it could not write these files: "SecondLife.exe" "dbghelp.dll" "cg.dll" "cgGL.dll" "fmod.dll" I believe I may have accidentally deleted these files while trying to clear space on my hard drive. Stupid move, I know so don't complain about it or tell me that it was stupid. Does anyone know how I can fix this?