I wouldn't trust that it's a safe file. I'd make sure you get rid of it. If Windows needs it, windows update should be able to fix itself. However, if it re-creates itself, that could also mean that it's a virus. I'd at least quarantine it, and then try to make sure it stays gone. Then try running Windows Update and see if you run into any problems. If you google for mswinup.exe, you only get 4 results... if it was a windows task, there would probably be 50 pages worth of results explaining that. Since there are only 4 results, I'd assume that it's a virus or spyware. Junk it!