PC World - Microsoft Corp. has rolled out fixes to improve Windows Vista's speed and reliability for the second time in two months. There are four separate updates, available now at Microsoft Web site. The updates address several operating system performance and stability problems, deal with a dozen Universal Serial Bus issues, improve Windows Media Player and patch Media Center. The updates will be distributed via Windows Update in October, the exact date not being known. Microsoft's next scheduled Windows Update releases are due out next Tuesday.