Yeah you must format. I tried the easy way out and just installed it over Vista. all my files were still in windows.old and it seemed to work fine, until about 1 hour later I got a bluescreen come up (where it reboots automatically). So I ignored it and carried on until about an hour later where I got another one. I kept getting one each day for a full week (was too busy to format that week) then on the weekend I lost it and decided to just format. Havent had a problem ever since
