Not certain on this myself but I did manage to find this, which seems to be worth a look through, specifically the last post. http://social.technet.microsoft.com/Forums/en/itproxpsp/thread/0f0a05b6-11a8-4f1f-a15c-4131c83fe2e5
You shouldn't need to completely re-install for one missing/corrupt file. You should be able to replace the file using either the recovery console or by performing a repair install as venjhammet suggested. Good luck!