Have you shut down NAV & other unnecessary background processes prior to installing SP2?
The answer to your 2nd Q, is yes. MS advises to first check at your PC manufacturers' websites - "As one of the steps to ensuring you have all of the support information you need to install SP2, we recommend visiting your PC manufacturer's Web site first and search for any information about SP2 that might apply to your computer" - from click here. Other relevant SP2 links: click here, click here & click here. G