1.放心大膽地安裝吧,係統亂了,可以system restore到安裝前
http://windows.microsoft.com/en-us/windows7/Create-a-restore-point
2.實在不放心,那就到Start-〉All Programs ->Maintenance -->Backup & Restore,可以做各種花樣的備份
http://windows.microsoft.com/en-CA/windows7/products/features/backup-and-restore